Method of making holographic images of drawing. RU patent 2511035.

FIELD: physics, optics.

SUBSTANCE: disclosed is a method of making holographic images of a drawing. The method involves converting the image of the drawing into digital raster; recording information on amplitude and phase characterising each raster point as an extended or point radiator; calculating the parameters of the recording radiation beam, for which elements of the digital raster of the image of the drawing are converted to digital raster of the future hologram; calculating the diffraction pattern at each point of the future hologram formed from the whole set of radiators; calculating the interference pattern resulting from interaction of the design diffraction pattern with the design wave front from a virtual reference point or extended radiation source, identical to the inverted real wave front of the source which will be used when forming the holographic image of the drawing. The obtained result is used as a modulation signal for the radiation beam used to form the diffraction structure of the hologram on a carrier, and a hologram is formed. The carrier is scanned line-by-line with a radiation beam which is modulated on intensity, at its diameter and intensity distribution inside the recording spot.

EFFECT: reduced deviation of the shape of the drawing from a given shape, high resolution and reliability of recording a temporary list of defects.

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obretenie relates to the field of microlithography, and can be industrial implemented, for example, in the manufacture of integrated circuits, holograms or structures with the generated for a given program relief with sub-micron resolution, for the manufacture of a hologram masks, and can to be used in the optical industry, for production of focusing, scattering and corrective optics elements; for example, kinoformat equipment, optical inspection shape aspherical surfaces, such as hologram compensators.

The creation of integrated circuits with the characteristic size of elements 0.1-0.01 mkm is the most promising direction of development of modern microelectronics. Technology of high-precision (with sub-micron and the micron tolerances) of manufacture of precision forms a three-dimensional relief can be industrial used, for example, when creating a mass technology of manufacturing of details of micro robots, high resolution elements and the Fresnel diffraction optics, as well as in other fields, there is a need in the functional layer of the product of three-dimensional picture set depth with high a resolution of its structures, for example, when making printing forms for production of banknotes and other securities.

From the resolution process microlithography defining the level of development of most branches of modern science and technology, depends crucially on further development of modern microelectronics. Microlithography involves coating the surface of a solid body (usually, a substrate of semiconductor material) layer of the material sensitive to the effects of the underlying stream-rays, optical radiation, or electron beam, which is used most often photoresist. Exposed photoresist through the template, usually called a mask that allows you to create the photoresist pattern corresponding to a given topology, such as topology layer created the integrated circuit.

Positioning accuracy best projection scanning systems (Steppers/scanners), produced by the world leader in this area of technological equipment for microelectronics - Dutch firm ASM Lithography, reaches 10 nm, which is clearly not enough to create VLSI with the characteristic size of elements of 20-30 nm. The lag opportunities boot from industry naturally, because development of stepper for submicron technologies requires three to five years, and its price at serial production, depending on the provided authorization is 25 to $ 125 million, not to mention the cost of development, component (in the case of the latest models) more billion dollars.

Currently, industry is the most common photomicrolithography (or photolithography). Provide her resolution Δ is determined by the wavelength λ applied radiation and numerical aperture NA projection system: Δx=k 1 λ/NA (Umora "Microlithography": in 2 hours Part 1: Per. from English. -M. Mir, 1990, s [1]). This dependence naturally stimulated the developers of the tendency to use more short-wave radiation sources and more vysokotemperaturnykh projection systems. As a result, over the last 40 years in the industrial projection photolithography has been a shift from mercury lamps with a characteristic wavelength of 365 nm to excimer lasers with a wavelength of 248 and 193 nm. Projection lenses modern Steppers reached 600-700 mm diameter and weigh more than 700 kg Besides, it is necessary to take into account the need to use immersion, ensure precise positioning and high-performance (up to 200 silicon wafers with a diameter of 300 mm, containing 125 zones blowout size 26 x 33 mm). All this has led to exponential growth of prices for modern high-resolution Steppers.

Increase the resolution, unfortunately, leads to a sharp decrease in the depth of focus F as F=±λ/2(NA) 2 [1, s], which reduces productivity and radical complexity to focus giant projection lenses, and so, again to increase the value of the stepper. Besides the regional effects limit the possibility of using aperture this lens when working with extreme resolution provided by the lens.

In the process of development projection photolithography the minimum size of the projected parts decreased in average by 30% every 2 years, which allowed every 18 months to double the number of transistors on integrated circuits (Moore's law). Currently used in industry "22 (limited) - 28-nanometer technology, allowing to create topological elements of integrated circuits resolution 22-28 nm, while the next frontier, according to experts, is the creation of projection systems and sources of radiation, and sustainable resolution on the level of 14 nm (currently there are already results obtained in experimental-industrial production), further promotion to permissions-10o nm require sources of extreme ultraviolet (EUV sources) or even move to soft x-rays. Currently intensively conducted experiments with microlithography on λ=13.5 nm. The first pilot installation, as reported in the developers forum of INTEL company (the leading world manufacturer of VLSI), was created and in 2002 it received transistors with a characteristic size of 50 nm. However, the cost of stepper even during production will be achieved, according to experts, 125 million dollars, and for debugging serial production of microprocessors with characteristic sizes of the elements at the level of 22 nm will be required according to the most optimistic estimates 5-6 years.

One of the most significant limitations of application photolithography is a limitation related to the diffraction from the edges mask (diffraction from the edges of the screen)used to obtain the desired projection of the image on the surface of the photoresist. This phenomenon, as increasing monochromaticity used radiation leads to a more and more noticeable deterioration of image quality, due to the appearance of diffraction maxima located at distances of about λ from the centre of the projected line. Given that currently the leading manufacturers uses a laser with a wavelength of λ=193 nm, it becomes obvious how important may be a restriction on the resolution introduced by diffraction on the edge of the mask.

Thus, the current projection device for create an image on a photosensitive layer have a number of disadvantages:

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

2) significant complexity of the design and technology of projecting devices with decreasing wavelength radiation used when projecting images on a photoresist;

3) the complexity of optical systems and technologies of manufacture of a projected mask object with decreasing wavelength used when projecting;

4) the sharp appreciation of technology and equipment in process of growth the degree of integration (reducing the characteristic size of topological elements critical layers of integrated circuits);

5) extremely low technological flexibility and very high costs of restructuring;

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

A method of obtaining the binary hologram in which a large number of areas transmission in the opaque film for the emission of material in accordance with their pre set/the calculated position, so that when the light of the obtained set of these areas bandwidth topographic image was formed at the specified distance from them (Limarko. "Basics of holography and coherent optics". ), Nauka, 1971, s-434 [2]). In this monograph examines the possibility of obtaining "numerical holograms", also called synthetic, artificial or binary hologram, and theory, characterized by brevity and clarity of mathematical description. However, a method of obtaining the binary holograms, when which image areas bandwidth receive, for example, graphically, and photographed with a significant decrease, it is not possible to obtain a sufficiently high image quality and high resolution, first of all, due to insufficient accuracy of manufacturing and insufficiently large number thus created areas of bandwidth.

A method of obtaining images on sensitive to the radiation of the material with the use of a hologram, which form on the surface sensitive to the radiation material spot illuminated by getting on his the surface image to be created when the lighting of coherent radiation source holograms, installed in front sensitive to the radiation material (GB 1331076 And, publ. 19.09.1973 [2]). However, a method of obtaining images on sensitive to the radiation the material with the use of a hologram is not possible to obtain high quality images due to the overlap of multiple diffraction orders, and high resolution owing to the impossibility of application is rather short-wave radiation sources.

A method of obtaining the binary holograms, known from RU 2262126 [3]. According to the description in the film material is opaque to radiation used to restore the image, you get a lot of areas of transmission in accordance with their specified or calculated size and position. In this advance get on sensitive to the radiation the material available on the film opaque material, the image specified many areas of bandwidth, and the image of each of which is accomplished by the formation of the total area of overlap spots flare, each of which provides a sensitive material dose radiation is less than E, then where E long - threshold dose of radiation that corresponds to the threshold sensitive to the radiation material, and the radiation dose received by sensitive to the radiation material in each total area of overlap spots exposure equal to or exceeds E. long. The spots of light are using located in front of surface sensitive to the radiation of the material of the two-dimensional matrix of emitters, each of which is designed with the ability to control the intensity of the outgoing radiation and contains, in at least one element for formation of the flux of radiation with the given size and shape of its cross-section, interconnected with the source, and when receiving each of the total area of overlap spots flare, before development, at least one, spot illumination of making up that total area of overlap spots flare provide navigation matrix emitters or/and sensitive to the radiation material in a plane parallel to the surface sensitive to the radiation material, in one direction or two mutually perpendicular directions, and then use the appropriate form processing in the film used opaque to radiation material the many fields of bandwidth.

The disadvantage of this method is the limitation of the structure of the obtained binary holograms, and : generated by elementary area of transmission can only be positioned on a regular grid, the steps which may not be less steps locations emitters in the matrix, which limits, respectively, the possibility to influence the quality parameters topographic image by changing structure of the hologram. Known method also does not account for the possible creation of a hologram as a set of areas of bandwidth in an environment that is transparent to radiation, forming a topographic image, or stripe pits in reflecting this radiation environment, or combinations of these options, which makes maximum use of the opportunities provided by topographic method for obtaining high quality images. Also known method does not consider the opportunities of holding up to making holograms adjustments its structure, taking into account the physical conditions of obtaining topographical image and performed to obtain the maximum possible quality of the latter.

Closest to the claimed by its technical nature and the achieved result is a method of making topographic images of the figure, known from RU 2396584 [4]. The method is implemented as follows. Original picture, for example, the image of an integrated circuit, or topology, is converted into a raster in digital form. The conversion is as follows: original picture in black and white image is placed in some coordinate system. In the particular case of figure may be two, when the image, for example, consists of white items on a black background, and in General grayscale when the image is composed of parts, with one of the pre-specified number of levels level of brightness, for example, from 0 to 255. In the same coordinate system place a fine mesh with the pre-programmed steps. In the area occupied by the figure, for each grid write down the coordinates of this site and the brightness of the picture at this point. If you want to play a drawing with a preset phase distribution of radiation on this figure, it is the distribution phase also is represented in the form of black and white, in the General case, grayscale, images, and also found in the same coordinate system. The list of four values: two coordinates, brightness and phase for all mesh nodes, located in the area occupied by the original figure presented, for example, in a list, vector or matrix, and is a raster in digital form. Thus, record information about amplitude and phase characterizing each raster point, as a point emitter. If you want to represent each raster point as long emitter, such as a circle or a square, then the coordinates of this point are the coordinates of the center extended emitter, the phase point is the phase in the center extended the emitter, and optionally sets the long form of the radiator, the distribution of amplitude and phase on its surface. Then calculate the diffraction pattern at each point of the future hologram created from the whole population of emitters-elements digital raster image of the figure. To do this, use a computer equipped with the corresponding software. Then expect an interference picture which will be received from between the settlement pattern of diffraction from settlement wave front from virtual reference source of the radiation wave front is identical converted wave front real radiation source, which will later be used to restore the images recorded on the hologram. The resulting data is used for the modulation of the radiation beam, which is used to record holograms on the media. As the source of radiation can be used lasers or sources of accelerated particles under the influence of which may change the properties of individual sections of irradiated media. As the latter can be used photoresist of some kind, sensitive to the radiation.

The disadvantage of this method is the difficulty and complexity of the calculation of the corrections to be made in the hologram to get it restored high quality images. The complexity of optimization of the hologram can dozens of times exceed the complexity of the initial calculation hologram mask. In addition, analysis of the structure of the synthesized thus hologram in which the transmission amplitude is formed by placing permeable elements of the same size (holes) with various weights, showed that this approach requires multiple exceeding the size of the hologram on the image size.

The claimed as an invention of the method of manufacture of holographic images of the figure is aimed at getting the picture with a high technological parameters, including reducing deviations geometry get picture from the set, increase the contrast of the resulting figure, the increased resolution, as well as on reducing the size hologram mask that is required to play the specified pattern.

To obtain a restored image of the picture with high technological parameters of the original figure is converted into a raster in digital form, write the information about amplitude and phase characterizing each raster point as long or point emitter, calculate the necessary parameters for writing beam radiation, which translate elements of digital raster image of the figure in the digital raster future hologram, they expect the diffraction pattern at each point of the future hologram created from the whole population of emitters - elements of digital raster image drawing, counting interference pattern obtained from between the settlement pattern of diffraction from settlement wave front from virtual reference point or extended radiation source, identical facing a real wave front the source that will be used when forming the holographic image of the picture, and then to reduce the variance of the geometry of the obtained picture from the set, increase the contrast of the resulting figure, increase resolution and reduce the size hologram mask, required to play the specified pattern, the digital raster hologram is converted into digital raster restored image of the picture and compare it with the original raster image of the picture, choose a measure of discrepancy, compare on this measure, and the results make the corrections in digital raster original image of figure, and then on the basis of adjusted raster image picture again relying digital raster holograms, and then use the result as a signal modulation of the radiation beam is used for the formation of diffraction patterns the hologram on the media.

Transformation of the original picture in the raster in digital form and record the information about amplitude And phase characterizing each raster point as long or point the emitter provides the ability to calculate the diffraction pattern generated by the figure, as the amount diffraction patterns are created all the elements, using the known solution for the diffraction problem (propagation of electromagnetic waves) for the above long or point emitter.

Progressive media scanning beam radiation allows recording to the media elements of its diffraction patterns zones with modified optical properties with a continuous distribution of the value of the specified optical properties (for example, transmittance, reflectance, phase shift) within each zone.

Modulation of the beam intensity he diameter and distribution of intensity inside the recording spot provides the ability to record on media using progressive scan areas modified optical properties that would have a very small size, approaching the size of the diffraction spots blur writing beam radiation and at the same time, it is an arbitrary distribution of changeable optical properties within.

Convert digital raster hologram in the digital raster restored image of the picture and compare it with the original raster image of the figure, the choice of the measure of discrepancy, comparison of this measure and making the correction in digital raster original image of figure on the comparison allows calculations without the experiment, to evaluate and improve the quality of the picture.

Convert digital raster hologram in the digital raster restored image drawing and subsequent calculation spots blur - digital raster restored image of the picture, consisting of one point, making the correction in digital raster original image of figure to each point of this raster by adding taken with a certain factor in advance designed digital raster spots blur transferred by the center to this point, you can simplify and accelerate the process of calculation of the final digital raster hologram.

Acceleration is attributable to the following.

Example 1. In the most General case, the method is implemented as follows. Original picture, for example, a picture of an integrated circuit, or topology, is converted into a raster in digital form. The conversion is as follows: original picture in black and white image is placed in some coordinate system. In the particular case, the figure may be two, when the image, for example, consists of white items on a black background, and in General grayscale when the image is composed of parts, with one of the pre-specified number of levels level of brightness, for example, from 0 to 255. In the same coordinate system place a fine mesh with the pre-programmed steps. In the area occupied by the figure, for each grid write down the coordinates of this site and the brightness of the picture at this point. If you want to play a drawing with a preset phase distribution of radiation on this figure, it is the distribution phase also is represented in the form of black and white, in the General case, grayscale, images, and also found in the same coordinate system. The list of four values: two coordinates, brightness and phase for all mesh nodes, located in the area occupied by the original figure presented, for example, in a list, vector or matrix, and is a raster in digital form. Thus, record information about amplitude and phase characterizing each raster point as a point emitter. If you want to represent each raster point as long emitter, such as a circle or a square, then the coordinates of this point are the coordinates of the center extended emitter, brightness point is the brightness in the center extended the emitter, the phase point is the phase in the center extended the emitter, and optionally sets the long form of the radiator, the distribution of amplitude and phase on its surface.

Then the figure specified in digital form, is used to compute the digital raster optimized electromagnetic field on the surface of the photoresist, which use a computer equipped with the corresponding software.

Then calculate the diffraction pattern at each point of the future hologram created from the whole population virtual emitters - the elements of digital raster optimized electromagnetic field. To do this, use a computer equipped with the corresponding software.

Then expect an interference picture will be obtained from the interaction of the settlement pattern of diffraction from settlement wave front from virtual reference source of the radiation wave front is identical converted wave front real source of radiation, which in the future will be used to restore the image recorded on the hologram.

The resulting data is used for the modulation of the radiation beam, which is used to record holograms on the media. As the source of radiation can be used lasers or sources of accelerated particles under the influence of which may change the properties of individual sections of irradiated media. As the latter can be used resist any type, sensitive to the radiation.

Example 2. As the source of the graphic image sets of different geometric figures (squares, triangles and circles connected by straight lines). Geometric figures had different dimensions (4-6 mm), and the lines connecting them, of different thickness (1-1 .5 mm). The original figure was converted to digital raster using the following : Original picture in black and white grayscale image is placed in some coordinate system. In the same coordinate system place a fine mesh with the pre-programmed steps. In the area occupied by the figure, for each grid write down the coordinates of this site and the brightness of the picture at this point. If you want to play a drawing with a preset phase distribution of radiation on this figure, it is the distribution phase also is represented in the form of black and white, in the General case, grayscale, images, and also found in the same coordinate system. The list of four values: two coordinates, brightness and phase for all mesh nodes, located in the area occupied by the original figure presented, for example, in a list, vector or matrix, and is a raster in digital form.

Thus wrote the information about amplitude and phase characterizing each raster point as a point emitter.

Then hoped interference pattern that will be received from the interaction of the settlement pattern of diffraction from settlement wave front from virtual reference source of the radiation wave front is identical converted wave front real source radiation, which will later be used to restore the image recorded on the hologram. The calculation was carried out by calculating the complex amplitude of the radiation generated reference source in each point of the hologram and the subsequent addition of this amplitude with complex amplitude calculated diffraction pattern.

Obtained data were used for the modulation of the radiation beam, which was used to record holograms on the media.

As a carrier of the hologram was used deposited on a transparent quartz substrate layer of photoresist mark Shipley 1808 thickness of 0.4 microns, which is exhibited in a special installation, using as a source of radiation of a He-Cd laser brands of PLASMA with a capacity of 90 mW wave length radiation 0,442 microns.

Included with the installation of optical elements with Electromechanical actuators, provided the controlled progressive media scanning beam radiation intensity modulated, he diameter and distribution of intensity inside the recording spots. Control of Electromechanical actuators are carried out from a personal computer equipped with the corresponding software, which uses as input digital raster final hologram.

After the exposure media hologram was formed layer of photoresist with continuous variable illumination, which is then processed to remove the exposed areas. As a result, the media hologram formed microrelief with the profile corresponding to the held for imaging.

Then, using ion plasma etching profile processed photoresist tolerated in a quartz substrate.

Recorded on the hologram image was restored with the help of the radiation source, which was used He-Cd laser brands of PLASMA with a capacity of 90 mW wave length radiation 0,442 microns.

The result is a restored image of the original graphic, reduced 10,000 times, the typical size of geometric figures were 0.4-0.6 microns.

Example 3. As the source of the graphic image sets of different geometric figures (squares, triangles and circles connected by straight lines). Geometrical shapes and lines, connecting them had different sizes and thicknesses (2.5-6 mm).

The original figure was converted to digital raster using the following : Original picture in black and white grayscale image is placed in some coordinate system. In the same coordinate system place a fine mesh with the pre-programmed steps. In the area occupied by the figure, for each grid write down the coordinates of this site and the brightness of the picture at this point. The distribution phase also is represented in the form of black and white, grayscale and also placed in the same coordinate system. The list of four values: two coordinates, brightness and phase for all mesh nodes, located in the area occupied by the original figure presented, for example, in a list, vector or matrix, and is a raster in digital form. Thus wrote the information about amplitude and phase characterizing each raster point as a point emitter.

Then calculate the diffraction pattern at each point of the future hologram created from the whole population of emitters - elements digital raster image of the figure. We used the method of calculation of the amounts of convolution type with the use of Fourier transform and use of algorithm of fast Fourier transform. For its implementation, used a computer equipped with the corresponding software.

Then hoped digital raster main holographic interference pattern that will be received from the interaction of the settlement pattern of diffraction from settlement wave front from virtual reference source of the radiation wave front is identical converted wave front real source of radiation, which in the future will be used to restore the image recorded on the hologram. The calculation was carried out by calculating the complex amplitude of the radiation generated reference source in each point of the hologram and the addition of this amplitude with complex amplitude calculated diffraction pattern.

Then counted in the same way digital raster subsidiary of the hologram, which as the source of the figure used the image consisting of one shape with dimensions less than 1/2 wavelength of the radiation source.

Then counted the image to be restored obtained with the method above digital raster master hologram. The calculation was carried out by

- calculation complex amplitude of the radiation created during recovery of each point of the hologram;

- calculate the diffraction pattern at each point of the virtual restored picture created from the whole population of emitters - elements digital raster hologram. We used the method of calculation of the amounts of convolution type with the use of Fourier transform and use of algorithm of fast Fourier transform. For its implementation, used a computer equipped with the corresponding software.

Then also hoped digital rasters of amplitude and phase spots blur the image to be restored with digital raster subsidiary of the hologram.

Then calculate the measure discrepancies is the sum of the moduli of differences in the intensity of all points raster original image and the virtual restored in the digital form of the digital raster master hologram.

Then at each point digital raster virtual restored picture was added multiplied by a coefficient digital raster spots blur, moved his heart to this point.

The coefficients were selected by minimizing the above measures mismatch with the help of gradient methods of optimization. For its implementation, used a computer equipped with the corresponding software.

Then, using the same way that previously were calculated digital rasters main and auxiliary holograms, hoped digital raster final hologram, taking over the original image digital raster optimized picture - the result of the optimization method.

The obtained data - digital raster final hologram is used for the modulation of the radiation beam, which were used to record holograms on the media.

As a carrier of the hologram was used deposited on a transparent quartz substrate layer of photoresist brand Shipley1808 thickness 0,4 mkm, which was exhibited in a special facility using as the source of the radiation of a He-Cd laser brands of PLASMA with a capacity of 90 mW wave length radiation 0,442 microns.

Included with the installation of optical elements with Electromechanical actuators, provided the controlled progressive media scanning beam radiation intensity modulated, he diameter and distribution of intensity inside the recording spots. Control of Electromechanical actuators are carried out from a personal computer equipped with the corresponding software, which uses as input digital raster final hologram.

After the exposure media hologram was formed layer of photoresist with continuous variable illumination, which is then processed to remove the exposed areas. As a result, the media hologram formed microrelief with the profile corresponding to the held for imaging.

Then, using ion plasma etching profile processed photoresist tolerated in a quartz substrate.

Recorded on the hologram image was restored with the help of the radiation source, which was used He-Cd laser brands of PLASMA with a capacity of 90 mW wave length radiation 0,442 microns.

The result is a restored image of the original graphic, reduced 10,000 times, the typical size of topological elements accounting for 0.25-0.5 micron.

1. Method of manufacture of holographic images of the figure, including its transformation into a raster digital recording information about amplitude and phase characterizing each raster point as long or point emitter, calculation of required parameters for writing beam radiation, which translate elements of digital raster image of the figure in the digital raster future hologram, they expect the diffraction pattern at each point of the future hologram created from the whole population of emitters - elements digital raster image drawing, counting interference pattern obtained from between the settlement pattern of diffraction from settlement wave front from virtual reference point or extended radiation source, identical facing a real wave front of the source that will be used when forming the holographic image of the picture, use the result as a signal modulation of the beam that is used to the formation of diffraction patterns of the hologram on the media, and create a hologram that is different

they use progressive media scanning beam radiation intensity modulated, he diameter and distribution of intensity inside the recording spots.

2. The method according to claim 1, different

the fact that digital raster hologram is converted into digital raster restored image of the picture and compare it with the original raster image of the picture, choose a measure of discrepancy, compare on this measure, and the results make the corrections in the digital raster source image drawing.

3. The method of claim 2, characterized

the fact that digital raster hologram is converted into digital raster restored image of the figure, expect spot blur - digital raster restored image of the picture, consisting of one point, make the corrections in digital raster original image of figure to each point of this raster by adding taken by a factor of pre-calculated digital raster spots blur transferred by the center to this point, and then calculate the final digital raster hologram.

4. The method according to claim 3 different

the fact that for the calculation of the coefficients are using any of the gradient methods.