RU2738112C1 - Use of polysaccharide compound in lithography - Google Patents

Abstract

FIELD: nanotechnology.

SUBSTANCE: invention relates to micro- and nanotechnology, particularly to use of chitosan polysaccharide and compounds thereof as resists for electron-beam lithography and photolithography for making micro- and nano-electronic and optical components. Invention relates to a method of exposing exposed areas of a film of chitosan, a salt or derivative thereof deposited on a substrate, involving bringing a film of chitosan, its salt or derivative thereof, which is applied on the substrate and subjected to exposure, into contact with a solution containing at least one transition element.

EFFECT: disclosed is use of polysaccharide compound in lithography.

44 cl, 11 dwg, 14 ex

Description

Technology area

The invention relates to the field of micro- and nanotechnology, in particular to the use of compounds of polysaccharides in lithography for the manufacture of micro- and nano-electronic and optical components.

State of the art

At present, lithography is widely used to obtain micro- and nanostructures. Lithography in micro- and nanoelectronics is a method of forming a structure on a substrate, which includes applying a resist material to a substrate, exposing the applied resist to electromagnetic radiation or an electron flow (exposure), and then developing the exposed areas of the resist in a special solution.

Resists based on polymethyl methacrylate (PMMA) and its derivatives, epoxy and other resins, organic polymers and azides, rubber, polybutene, etc. are often used as resists for photolithography and electron-beam lithography. These methods are characterized by high resolution and allow one to obtain structures of small dimensions ...

However, these methods of lithography using traditional resists include the stages of heating and the use of materials and liquids (in particular, for the development of the resist and its removal), which relate to organic solvents, concentrated solutions of acids and alkalis, and, accordingly, do not allow to obtain components based on sensitive objects, in particular such as organic polymers, biological structures, for example, protein-based nanowires, DNA, artificial peptide systems, organic superconductors and semiconductors, which are not able to withstand some or all of the processing stages and retain their original structure.

Described are methods of lithography using materials of biological origin as resists, and water as a developer.

The known method of electron beam lithography using a film of silk protein (fibroin) as a resist (Kim S. et al. "All-water-based electron-beam lithography using silk as a resist", Nature Nanotechnology, volume 9, pages 306 -310 (2014)), and water as a developer. Aqueous solutions of fibroin are mechanically unstable, therefore it is rather difficult to work with them, and during the development process the resist is not completely removed from the exposed areas. In addition, plasma, ionic liquids or concentrated acid solutions must be used to remove unexposed resist.

Document WO2016162638 A1 describes the use of chitosan and / or alginates as resists for lithography. Chitosan was applied to a support from an aqueous acid solution, dried to remove water, exposed, the exposed areas were developed with an aqueous solution of an acid (acetic, citric, or tartaric), while unexposed areas were removed using oxygen plasma or a solution of concentrated sulfuric acid with hydrogen peroxide.

M. Caillau et al. “Fifty nanometer lines patterned into silica using water developable chitosan bioresist and electron beam lithography”, Journal of Vacuum Science & Technology B, 35, 06GE01 (2017) describes the use of chitosan as a positive resist for electron beam lithography. A resist film was prepared from chitosan dissolved in an aqueous solution of acetic acid and dried (at a temperature of 100 ° C for 1 min). The exposed areas were developed with water, and the removal of the unexposed resist film was performed using oxygen plasma.

S. Voznesenskiy et al. "Study of Biopolymer Chitosan as Resist for Submicron Electronic Lithography", Solid State Phenomena, Vol. 213 (2014), pp. 180-185, also describes the use of chitosan in electron beam lithography. Chitosan was dissolved in 2.5% acetic acid solution and a film was formed from the resulting solution, which was subsequently treated with 3% ammonia solution for 10 minutes to neutralize the film and washed with water. The exposed areas of the chitosan film were developed using water, while incomplete clearing of the exposed areas from the resist material was observed. If it was necessary to remove the unexposed resist film from the substrate, either aggressive solvents such as concentrated acids or oxygen plasma were required.

Existing techniques based on water-soluble resists are poorly applicable for the manufacture of micro- and nanoelectronic and optical components based on sensitive organic objects, since they use incompatible solvents (for example, concentrated acid solutions) or plasma. In addition, the incomplete removal of the resist after development makes it difficult (for example, liquid etching) or makes it impossible (for example, explosive lithography) further technological stages of obtaining structures.

Thus, there is a need to develop methods for producing micro- and nano-electronic and optical components suitable for obtaining micro- and nano-electronic and optical components based on sensitive materials, in particular, on the surface of biological or organic objects.

Disclosure of the essence of the invention

One of the objectives of the present invention is to provide a method for producing micro- and / or nano-electronic and / or optical components, which would eliminate at least some of the disadvantages of known methods for producing micro- and nano-electronic and optical components, or to offer a useful alternative to existing methods ...

In particular, one of the objects of the present invention is to provide a method for producing micro- or nano-electronic or optical components that would be suitable for use on substrates sensitive to aggressive influences, for example, for use on substrates that are biological objects.

One particular object of the present invention is to provide a method for developing exposed areas of a resist deposited on a substrate, in particular during the production of micro- and nano-electronic and optical components.

Another particular object of the present invention is to provide a method for forming micro- or nano-electronic or optical components.

Below will be described embodiments of the present invention, indicating the achieved technical results. Also, after reading this description, the specialist will understand other achieved technical results and problems to be solved.

In a first aspect, the present invention relates to a method for developing exposed regions of a polysaccharide compound film applied to a substrate, comprising contacting the polysaccharide compound film with a solution containing at least one transition element.

One of the technical results achieved by the present invention is to increase the removal rate of resist material from exposed areas relative to the removal rate of resist from unexposed areas, i.e. increasing the selectivity of removing the resist from exposed areas relative to unexposed areas, in comparison with known technical solutions using water and other resists with high compatibility with organic or biological objects. In particular, the proposed method allows for complete removal of the resist from the exposed areas with minimal dissolution of the resist in the unexposed areas.

Increasing the selectivity of removing the resist from the exposed areas relative to the unexposed areas increases the contrast of the process and, therefore, improves the degree of correspondence of the resulting structure on the substrate surface to the exposed image.

The proposed method is fast, simple, compatible with sensitive substrates, which are adversely affected by such factors as heating, the action of concentrated solutions of acids and alkalis, organic solvents and plasma. Also, the proposed method reduces the negative impact on the environment. In particular, a resist suitable for use in the present invention can be obtained from food waste (eg, shrimp farming). At the same time, the negative impact on the environment is reduced due to the fact that the processed products have a safe disposal route.

In addition, the proposed method provides the possibility of explosive (reverse) lithography, as well as direct manufacture of microcontacts and good adhesion of metals in the developed areas.

In one particular embodiment, the exposed areas are areas of the film irradiated with a stream of elementary particles, preferably an electron stream, and / or electromagnetic radiation, preferably deep UV radiation, extreme UV radiation, gamma radiation or X-rays.

In another particular embodiment, the polysaccharide compound film applied to the substrate has a thickness of 20 to 190 nm, preferably 50 to 160 nm, more preferably 90 to 150 nm. With a film thickness in the indicated ranges, an additional increase in contrast is provided, which leads to an increase in the degree of correspondence of the resulting structures on the substrate to the exposed image.

In another particular embodiment, the polysaccharide compound is a polysaccharide or its amino derivative, nitro derivative, sulfo derivative, halogen derivative, phosphoric acid derivative, ether, ester or salt.

In another particular embodiment, the polysaccharide compound is a copolymer which, together with saccharide monomer units, also contains non-saccharide monomer units.

In another more particular embodiment, the polysaccharide compound is a chitosan compound, a cellulose compound, in particular their salts or another derivative, in particular chitosan, cellulose, beelosan.

In another more specific embodiment, the salt is a salt of a monobasic, dibasic, tribasic, or tetrabasic acid.

In another more particular embodiment, the salt is an organic acid salt, in particular a carboxylic acid salt, in particular a salt of formic, acetic or propionic acid, or mixtures thereof.

In another more specific embodiment, the chitosan salt or other chitosan derivative is selected from the group consisting of acetate, formate, lactate, glycolate, succinate, chloride, chitosan citrate, phthaloylchitosan, carboxymethylchitosan, succinylchitosan.

In another particular embodiment, the transition element is a d-element or f-element.

In another particular embodiment, the transition element is a fourth period transition element, a fifth period transition element, a sixth period transition element, or a seventh period transition element.

In another particular embodiment, the transition element is selected from the group consisting of zinc, nickel, copper, cobalt, iron.

A solution containing at least one transition element may contain a mixture of two or more different transition elements.

In another particular embodiment, the solution containing at least one transition element is a solution in a protic solvent, in particular in water, or in a mixture of solvents containing one or more protic solvents. The solvent can be an inorganic solvent, an organic solvent, or a mixture thereof. It is also possible to use a polar aprotic solvent, possibly in a mixture with other solvents.

In another more specific embodiment, the solution containing at least one transition element is a solution in a polar aprotic solvent or in a mixture of solvents containing a polar aprotic solvent.

The solvent for preparing a solution containing at least one transition element must also dissolve the polysaccharide compound, in particular, it must dissolve it after exposure to the polysaccharide compound film.

In another particular embodiment, the solution containing at least one transition element is a salt solution of at least one transition element.

In another particular embodiment, the salt of at least one transition element is selected from the group consisting of an inorganic acid salt and an organic acid salt. Non-limiting examples of an inorganic acid salt are chloride, nitrate, sulfate. Non-limiting examples of an organic acid salt are formate, acetate. It is also possible to use mixtures of two or more different salts as well as mixed salts such as Mohr's salt (ammonium-iron (II) sulfate).

In another more specific embodiment, the salt of at least one transition element is selected from the group consisting of chloride, nitrate, sulfate, formate, acetate, Mohr's salt (ammonium-iron (II) sulfate).

In another particular embodiment, the concentration of at least one transition element in solution is at least 1 mM, preferably at least 20 mM, more preferably at least 60 mM, even more preferably at least 200 mM. Increasing the concentration of the transition element additionally increases the selectivity of removing the resist from the exposed areas relative to the unexposed areas and the process contrast. In this case, the maximum concentration of the transition element is not particularly limited and can be selected, for example, on the basis of solubility or the ratio of costs and the achieved effect. Non-limiting examples of maximum concentration are 400 mM, 1M, 5M.

In another particular embodiment, the solution containing at least one transition element has a pH of 4 to 7.5, preferably about 5.5. Increasing the pH further increases the selectivity of removing the resist from the exposed areas relative to the unexposed areas, but at the same time reduces the dissolution rate of the exposed resist, which, on the contrary, increases with decreasing pH. Thus, it is possible to adjust the pH value depending on the desired selectivity and dissolution rate of the exposed resist. The pH range from 5 to 6.5 is a particular preferred embodiment that simultaneously achieves high selectivity and dissolution rates. It should be noted that the dissolution rate of the exposed resist at high pH values can be increased by increasing the radiation dose during exposure. Thus, an acceptable pH value can be higher than 6.5, for example, up to 7.5 or up to 9. Also, depending on the radiation dose, acceptable selectivity values can be obtained at a pH lower than 5, for example, from 4 or from 4, 5.

In another particular embodiment, the solution containing at least one transition element further contains organic substances, in particular solvents, polymers, surfactants. In a more specific embodiment, the solvent is an alcohol.

In another particular embodiment, contacting the film with a solution containing at least one transition element is carried out over a period of 10 seconds to 60 minutes, preferably 5 to 10 minutes, most preferably about 5 minutes. Increasing the contact time can improve the removal of resist from exposed areas, but longer contact times can lead to a decrease in film thickness in unexposed areas. Thus, it is possible to choose the value of the contact time depending on the required degree of removal of the resist from the exposed areas and the residual film thickness in the unexposed areas.

In another particular embodiment, the proposed method further includes the step of bringing the film into contact with a second solution containing at least one second transition element different from the first.

In another more specific embodiment, the method of the invention comprises sequentially bringing a film of a polysaccharide compound into contact with a nickel chloride solution and a nickel sulfate solution, preferably an aqueous nickel chloride solution and an aqueous nickel sulfate solution. The specified particular combination of stages allows to further increase the selectivity and contrast of the process, which ensures fast and complete removal of the resist material from the exposed areas and the absence of dissolution of the unexposed resist.

In another particular embodiment, the proposed method, after bringing the film into contact with a solution containing at least one transition element, further comprises the step of washing the film. Rinsing the resist film removes residual solution containing at least one transition element. Rinsing of the resist film is carried out with a suitable solvent, in particular suitable for removing residual solution containing at least one transition element. In a particular embodiment, the solvent is a protic solvent, preferably water, or a mixture of solvents containing one or more protic solvents. The solvent can be an inorganic solvent, an organic solvent, or a mixture thereof. It is also possible to use a polar aprotic solvent, possibly in a mixture with other solvents.

In a particular embodiment, the washing step is carried out over a period of 10 to 60 seconds. With the specified duration of the washing step, the degree of purification of the developed area from the exposed resist and residues of the transition element salt increases, and the dissolution of the unexposed resist film is minimized. With a longer contact of the resist film with water, in particular 10 min, the developed area is completely cleared, and at the same time, the latter begin to wash out from the area of the unexposed resist of the polysaccharide compound chelated with transition element ions, as a result of which the dissolution of the unexposed resist can be observed.

In another particular embodiment, the proposed method further comprises a drying step.

In another particular embodiment, the substrate is or contains carbon nanotubes, organic semiconductors, protein, lipid structures, DNA, biopolymer fibers, bacterial nanowires on its surface, or any combination thereof.

In one particular embodiment, the proposed method comprises sequentially the following steps:

- bringing the chitosan compound film into contact with about 400 mM aqueous solution of NiCl ₂ for about 5 minutes at a pH of about 5.5;

- bringing the chitosan compound film into contact with about 400 mM NiSO ₄ aqueous solution for about 5 minutes at a pH of about 5.5;

- rinsing with water for about 30 seconds;

- drying.

In a second aspect, the present invention relates to the use of a solution containing at least one transition element as a developer of exposed areas of a polysaccharide compound film.

The second aspect can be characterized by private variants of implementation, similar to private variants of implementation of the remaining aspects of the present invention.

In a third aspect, the present invention relates to a method for forming at least one component on a substrate, comprising the following steps:

a. applying a polysaccharide compound film to the substrate;

b. exposure to predetermined areas of said film with a stream of elementary particles and / or electromagnetic radiation (exposure);

from. developing exposed areas of the film by performing the method of the first aspect of the present invention to provide a masked substrate;

d. processing of a substrate with a mask applied to it by etching, deposition, alloying or any combination thereof;

e. removing the mask from the surface of the substrate to form at least one component on the substrate,

wherein the component is a micro- and / or nano-electronic and / or optical component.

According to the third aspect, the present invention makes it possible to increase the contrast of the process in comparison with the known processes using water-developing and other resists with high compatibility with organic or biological objects, and, therefore, provides an increase in the degree of correspondence of the formed structure of micro- or nano-electronic or optical components to the exposed image ...

The proposed method is also fast, simple, compatible with sensitive substrates that are adversely affected by such factors as heating, the action of concentrated solutions of acids and alkalis, organic solvents and plasma. Also, the proposed method reduces the negative impact on the environment.

In addition, the proposed method provides the possibility of explosive (reverse) lithography, and also provides for the implementation of direct manufacturing of microcontacts and good adhesion of metals in exposed areas after development.

In one particular embodiment, the particle flux is an electron flux and / or electromagnetic radiation is deep UV radiation, extreme UV radiation, gamma radiation, or X-rays.

In another particular embodiment, the film has a thickness of 20 to 190 nm, preferably 50 to 160 nm, more preferably 90 to 150 nm.

In another particular embodiment, applying a film to the substrate in step a. is carried out from a solution of a polysaccharide compound, which is pre-filtered or centrifuged. A polysaccharide compound solution is a solution in water, another inorganic solvent, or an organic solvent. As the solvent, a solvent is selected that dissolves the polysaccharide compound. Filtration and / or centrifugation of the polysaccharide compound solution prior to application to the substrate allows obtaining a homogeneous solution of the polysaccharide compound for film deposition and, accordingly, a homogeneous film without defects or with a minimum number of defects deposited on the substrate.

In another particular embodiment, the proposed method further comprises, after stage a: temperature treatment of the substrate, and / or treatment of the substrate with a solution containing at least one transition element, and / or treatment of the substrate with a film of the polysaccharide compound applied thereon with at least one inorganic or organic matter. Temperature treatment of the substrate after stage a. allows to significantly improve the resist properties of the polysaccharide compound. Treatment of the substrate with a solution containing at least one transition element makes it possible in principle to obtain a developed film that can be easily removed from the substrate and then transferred to another surface. In a more specific embodiment, the substrate treatment solution contains a salt of at least one transition element. Thus, in a particular embodiment, the present invention also relates to a developed film of a polysaccharide compound. Treatment of a substrate coated with a film of a polysaccharide compound with at least one inorganic or organic substance can change the properties of the film.

In another more specific embodiment, the organic material for treating the substrate after step a. is glycerin.

In another more specific embodiment, an inorganic substance for treating the substrate after step a. is a salt, in particular a carbonate salt. In another more specific embodiment, an inorganic substance for treating the substrate after step a. is an alkali metal salt, preferably an alkali metal carbonate, more preferably sodium carbonate Na ₂ CO ₃ .

In another particular embodiment, the etching is liquid etching or dry etching. This allows the surface of the substrate to be modified to obtain a desired surface structure.

In another particular embodiment, the removal of the mask from the surface of the substrate is carried out by exposure to water or a solution, preferably a solution containing no transition elements, more preferably an aqueous solution containing no transition elements. In another particular embodiment, the removal of the mask from the surface of the substrate is carried out by exposure to a solution containing the transition elements, preferably an aqueous solution containing the transition elements. Such removal methods provide complete removal of unexposed resist to obtain a structure on the surface of the substrate consistent with the projected image. Also, such removal methods allow explosive lithography to produce a pattern on the surface of the substrate in accordance with a predetermined pattern. Such methods of removal are characterized by simplicity, because unlike traditional methods of removing unexposed film, in particular using plasma, there is no need for equipment for generating plasma. Also, such methods are environmentally friendly, since there is no need to use toxic organic solvents, which are also traditionally used for removing unexposed film in the methods of the prior art. As a result, due to the absence of the need to use plasma, concentrated solutions of acids and alkalis and organic solvents to remove unexposed films, the proposed method is suitable for obtaining a structure on substrates that are sensitive to the action of plasma, concentrated solutions of acids and alkalis and organic solvents, in particular, substrates based on organic materials and / or materials of biological origin.

In another more specific embodiment, the solution containing no transition elements is a solution of an acid or salt other than a salt of a transition element, preferably an aqueous solution of an acid or salt other than a salt of a transition element. The presence of acid or salt can increase the rate of mask removal from the substrate surface. The solution containing no transition elements can be prepared in any suitable solvent. A polysaccharide compound solution is a solution in water, another inorganic solvent, or an organic solvent.

In another more particular embodiment, the acid solution has a concentration of 0.01 to 0.1 wt%.

The acid can have different basicities, for example, it can be monobasic, dibasic, tribasic, or tetra-basic. Accordingly, in another more specific embodiment, the acid is a monobasic, dibasic, tribasic, or tetrabasic acid.

In another more specific embodiment, the acid is an organic acid, in particular a carboxylic acid, in particular formic, acetic, propionic acid, or mixtures thereof.

In another more specific embodiment, the acid is weak. The use of a weak acid reduces the environmental impact while maintaining a high rate of mask removal from the substrate surface.

In an even more specific embodiment, the acid is formic acid.

In another more specific embodiment, the solution free of transition elements is an alkali metal carbonate solution, preferably at a concentration in the range of 50 to 150 mM. The use of low concentration alkali metal carbonate helps to reduce the environmental impact while maintaining a high removal rate of the mask from the substrate surface.

In another particular embodiment, the method for forming at least one component on a substrate is a lithography method, in particular an explosive (reverse) lithography method.

In another particular embodiment, the method steps for forming at least one component on a substrate are performed more than once to obtain a structure containing more than one layer of components.

In another particular embodiment, the substrate coated with at least one component is an integrated circuit.

The third aspect can be characterized by private variants of implementation, similar to private variants of implementation of the remaining aspects of the present invention.

In a fourth aspect, the present invention relates to a method for forming a mask of a polysaccharide compound comprising the following steps:

a. applying a polysaccharide compound film to the substrate;

b. exposure to predetermined areas of said film with a stream of elementary particles and / or electromagnetic radiation;

from. developing exposed areas of the film by performing the method of the first aspect of the present invention to provide a masked substrate.

In a particular embodiment, the method according to the fourth aspect of the present invention comprises after step a. treating the substrate with a solution containing a salt of at least one transition element. Treatment of the substrate with a solution containing the salt of at least one transition element makes it possible in principle to obtain a developed film that can be easily removed from the substrate and then transferred to another surface.

In a particular embodiment, the method according to the fourth aspect of the present invention further comprises the step of peeling off the developed film from the substrate and then transferring it to another surface.

The fourth aspect can be characterized by private variants of implementation, similar to private variants of implementation of the remaining aspects of the present invention.

In a fifth aspect, the present invention relates to a substrate coated with micro- and / or nano-electronic and / or optical components, in particular, elements of an integrated microcircuit, wherein the substrate is or contains carbon nanotubes, organic semiconductors, proteins, lipid structures, DNA, biopolymer fibers, bacterial nanowires, or any combination thereof.

In a sixth aspect, the present invention relates to a substrate coated with integrated circuit elements (micro- and / or nanoelectronic and / or optical components), which are applied by a method according to the third aspect of the present invention.

The substrate of the fifth and sixth aspects of the present invention can be designed for use as an electronic and / or optical component.

The fifth and sixth aspects can be characterized by private options for implementation, similar to private options for implementing other aspects of the present invention.

The essence of the invention is illustrated by the following drawings and examples of implementation.

Brief Description of Drawings

FIG. 1 (a) shows a diagram illustrating the proposed method for the development of a positive resist based on polysaccharide compounds: a solution of a polysaccharide compound is prepared and applied to the substrate surface, in this example by centrifugation, to obtain a thin film. Next, the film is irradiated with an electron beam or electromagnetic radiation, developed in a solution of salts of transition elements, washed and dried using an air stream. FIG. 1 (b) shows an optical image of the Skoltech logo after the development of a chitosan formate film with a molecular weight of 165 kDa, exposed to radiation from a femtosecond krypton-fluorine laser with a wavelength of 248 nm (deep ultraviolet (D-UV)); scale 50 microns.

FIG. 2 illustrates the basic principles of the developing process formulated for the present invention. FIG. 2 (a) shows the dependences of the diffusion time delay for two competing processes on the molecular weight of the polysaccharide compound in arbitrary units. In particular, the blue curve characterizes the dependence of the dissolution time of the polysaccharide compound on the molecular weight, obtained from the scaling model (Beth A. Miller-Chou, Jack L. Koenig “A review of polymer dissolution.” Prog. Polym. Sci. 28 (2003) 1223-1270) of the processes of unraveling of the higher macromolecular structure of the polymer chain, and the orange curve characterizes the dependence of the chelation time on the molecular weight, obtained from the model of ion passage through membranes (Nikolaos A Peppast, David L. Meadows “Macromolecular Structure and Solute Diffusion Membranes: An Overview Of Recent Theories. ”Journal of Membrane Science, 16 (1983) 361-377). The tab on the graph illustrates the qualitative dependence of the molecular weight of the polysaccharide on the exposure dose. FIG. 2 (a) shows that the development of the exposed resist is based on a balance between two conflicting processes: dissolution of the polymer (polysaccharide compound) and the formation of an insoluble complex of the polysaccharide compound with transition element ions. FIG. 2 (b) shows the dependence of the sensitivity of the resist in mC / cm ² on the pH of the developer solution. In this case, nickel was used as the transition metal, the concentration of the developer solution was 400 mM, and the development time was 10 minutes. This figure shows that the dissolution process, being much more sensitive to pH than the complexation process, leads to a change in the dose required to completely remove the exposed resist. The data was obtained for a developer concentration of 400 mM, and in the case of lowering the pH to a value of less than 5.0, strong dissolution of unexposed areas occurs. In the case of exceeding pH = 7.5, the dissolution of the polysaccharide becomes strongly suppressed, while all areas, exposed or not, are effectively chelated by ions of the transition element. FIG. 2 (c) shows the spectrum obtained by X-ray photoelectron spectroscopy of the sample after etching (a decrease in the film thickness by 25%). This spectrum shows the presence of nickel in the depth of the film both in the free and in the bound state, which confirms the deep penetration of ions of transition elements into the unexposed resist film. FIG. 2 (d) shows the dependence of the slope of the contrast curve at 60% of the height γ on the concentration of ions of transition elements in the developer solution, mM. The development time is 5 minutes, the pH is fixed at 5.5. It can be seen from the presented graph that under the remaining identical conditions the behavior of the resist contrast curves becomes more linear and canonical with an increase in the concentration of the developer solution.

FIG. 3 shows images of micro- and nanostructures obtained as a result of explosive lithography using chitosan acetate with a molecular weight of 700 kDa as a resist for electron-beam lithography. Development (except for the case shown in image (b)) was carried out in two stages: first, with a solution of nickel chloride with a concentration of 400 mM and pH 5.5 for 5 min, then with a solution of nickel sulfate with a concentration of 400 mM and pH 5.5 for 5 minutes. Then, metal was deposited: the lower Ti layer 1 nm thick and the upper Pd layer 11 nm thick. Next, the resist film was removed with a formic acid solution with a volume concentration of 0.1% with explosive lithography. Image (a) is an optical photograph of an array of structures obtained by explosive lithography in a dose test; scale 20 μm. The resulting structures consist of square elements with sides of 5 and 1 μm in combination with lines 250 nm thick and 1 μm long. This image illustrates that the structures formed are reproducible and not a random result. Moreover, they show the vicinity of the dose relative to the sensitivity in which the formation of structures is possible. Scanning electron microscope image (b) illustrates structures on the substrate surface produced by explosive lithography after development with a high concentration (2500 mM) transition element salt solution; scale 10 μm. The width of the narrowest lines is about 100 nm. As can be seen, the development of a high concentration transition element with a salt solution can achieve a fairly high resolution. Image (c) shows the critical dimension obtained as a result of explosive lithography under the conditions described above; scale 1 μm. This image shows that under the above development conditions, 200 nm (linewidth) elements can be obtained at a distance of about 500 nm from each other. Image (d) shows a single line from the array of lines shown in image (c); scale 150 nm.

FIG. 4 shows the results of the development of films of chitosan acetate of different thicknesses (90 and 200 nm) exposed under the same conditions. It can be seen that, at a film thickness of 200 nm, the edges of the structure are inhomogeneous and smoothed; the structure differs significantly from the specified template in the dose range at which the resist is completely removed from the exposed area during development. With increasing thickness, apparently due to the inhomogeneity of diffusion of the chelating component, this difference increases.

FIG. 5 shows the results of the development of films of chitosan acetate of different molecular weights (20, 65, 165, 200, and 700 kDa) during the dose test. LD corresponds to a test in which the exposure dose changes in a low dose range (25-750 μC / cm ² , current 50 pA), HD corresponds to a test in which the exposure dose changes in a high dose range (500-15000 μC / cm ² , current 10 nA). As can be seen, the molecular weight of the polysaccharide compound practically does not affect the properties of the polysaccharide compound as a resist, and for each molecular weight there is a dose range in which, as a result of development, complete removal of the exposed resist and the absence of dissolution of the unexposed one is ensured.

FIG. 6 shows the results of the development in accordance with the present invention of films from various chitosan compounds: CA - chitosan acetate, CF - chitosan formate, CG - chitosan glycolate, CL - chitosan lactate, CS - chitosan succinate, CMC - carboxymethylchitosan. The presented data show that all the studied compounds of chitosan make it possible to ensure complete removal of the exposed resist as a result of development and the absence of dissolution of the unexposed one.

FIG. 7 shows the effect of removing impurities from a solution of chitosan acetate before applying it to a substrate on the morphology of the film obtained from it. Photo (a) corresponds to a film of chitosan acetate obtained from solution without additional purification. Photo (b) corresponds to a chitosan acetate film obtained from a solution centrifuged at 13,200 rpm (15,000 g) for 10 minutes. Photo (c) corresponds to a film of chitosan acetate obtained from a solution centrifuged in a filter tube with a pore diameter of 100 nm. Photo (d) corresponds to a chitosan acetate film obtained from a solution filtered through a 200 nm syringe filter. As can be seen, the chitosan acetate film obtained from a solution filtered through a syringe filter is characterized by the highest homogeneity and the minimum number of defects.

FIG. 8 shows the structures of the array of elements of the dose test obtained as a result of the development of the exposed film of chitosan acetate with solutions of different salts of transition elements, the deposition of a metal with a thickness of 20 nm and the removal of the unexposed film: nickel chloride, nitrate, acetate, sulfate and formate, copper sulfate, cobalt acetate separately or in combination with a surfactant, Mohr's salts. This image shows that in principle it is possible to use various transition elements to create a developer. Each individual transition element, the corresponding salt cation, organic or inorganic additives to the developer composition affects the process and requires, in order to achieve the best effect, the adjustment of the development protocol: selection of concentrations, pH, processing time.

FIG. 9 shows photographs obtained with an optical microscope, illustrating the effect of the pH of the developer solution on the sensitivity and contrast of the resist. The data are presented for a film of chitosan acetate with a molecular weight of 65 kDa, a developer based on nickel chloride. a) pH 5.0, b) pH 5.5, c) pH 6.0, d) pH 6.5, e) pH 7.0, f) pH 7.5. All images show the same area of the dose test. Based on this test, the graph shown in FIG. 2 (b).

FIG. 10 shows photographs obtained with an optical microscope illustrating the effect of the washing step after the development of the film with solutions of salts of transition elements. Each photograph shows a standard dose test with an increasing exposure dose. Photo (a) corresponds to development with a nickel-based developer without rinsing. Photo (b) corresponds to development with a water wash for 30 seconds. Photo (c) corresponds to development with water rinsing for 10 minutes. As can be seen, in the case of prolonged washing after development, a large deviation of the developed structure from the exposed template is observed, since the ions of transition elements chelating the molecules of polysaccharide compounds are washed out from the film of unexposed resist, and, accordingly, the unexposed regions dissolve.

FIG. 11 shows the characteristic curves describing the dependence of the relative residual thickness of the exposed film (h / h₀) (the ratio of the residual resist thickness h to the initial thickness h₀) a resist based on chitosan acetate with a molecular weight of 65 kDa after development from the dose it received (D) by exposure in logarithmic coordinates. The tangent of the slope of the tangent to the characteristic curve is called the resist contrast (γ). Plot (a) shows the characteristic curve for the resist after development with a 5 mM nickel salt solution. Plot (b) shows the characteristic curve for the resist after development with a 2500 mM nickel salt solution. Plots (c) and (d) show the resist after development only with a solution of nickel chloride with a concentration of 400 mM for 10 min (graph (c)) and a solution of nickel chloride with a concentration of 400 mM for 5 min, followed by treatment with a solution of nickel sulfate ( two-stage development) with a concentration of 400 mM for 5 min (graph (d)). From the presented data, it can be seen that in the graphs (a) and (c) there are sections for which the tangent of the angle of inclination of the tangent (in particular, γ₆₀ - the tangent of the angle of inclination of the tangent at a relative residual thickness of 60%) is less than 0.6. It can be seen that an increase in the concentration of the transition element ion in the composition of the developer solution (from 5 mM in the graph (a) to 2500 mM in the graph (b)) and a change in the anion in the developer solution (only chloride ion in the graph (c) and the combination chloride ion and sulfate ion in the plot (d)) leads to an increase in the contrast of the resist.

Implementation of the invention

The following description sets forth the means and methods by which the present invention can be carried out, as well as examples of its implementation.

When characterizing some quantitative traits, the term "about" is used. This term reflects the uncertainty that is inherent in the measurement of any quantitative characteristic, and denotes a range that is a quantitative characteristic ± measurement error. The measurement error may be 10%, more preferably 5%.

The term "polysaccharide" used to describe the present invention refers to a high molecular weight compound containing monosaccharide residues, at least some of which are linked by a glycosidic bond. In a particular case, the polysaccharide consists of monosaccharide residues linked by a glycosidic bond.

The term "polysaccharide compound" refers both to the polysaccharide itself and to its derivatives in which the polysaccharide skeleton is preserved. Non-limiting examples of polysaccharide derivatives are: amino derivatives, nitro derivatives, sulfo derivatives, halogen derivatives, phosphoric acid derivatives, ethers and esters, salts. The term "polysaccharide compound" also includes copolymers which, together with saccharide monomer units, also contain non-saccharide monomer units. The polysaccharide compound is characterized by the fact that its average molecular weight decreases under the influence of radiation, as well as the ability to form chelates with transition elements.

Specific non-limiting examples of polysaccharide compounds are chitosan, beelosan (apizan), cellulose, starch, dextrin, pectin, galactomannan, alginic acid, their salts and other derivatives.

The term "chitosan" used to describe the present invention refers to a naturally occurring polysaccharide consisting of two types of monomer units, D-glucosamine and N-acetyl-D-glucosamine, linked by a β- (1 → 4) -glycosidic bond. The number of N-acetyl-D-glucosamine units corresponds to the degree of acetylation, which is a characteristic of chitosan. Chitosan is a non-toxic, biocompatible and biodegradable polymer.

The term "beelosan (apizan)" as used to describe the present invention refers to chitosan isolated from the chitinous cover of bees.

The term "transition element" used to describe the present invention refers to chemical elements in the atoms of which in the electron shell the valence electrons with the highest energies occupy the d and f orbitals. In the periodic table of chemical elements, the transition elements are in groups 3-12 in periods 4-7.

The term "inorganic solvent" as used to describe the present invention refers to any known inorganic solvent. Specific non-limiting examples of inorganic solvents include water, ammonia, inorganic acids, aqueous solutions of inorganic salts.

The term "organic solvent" as used to describe the present invention refers to any known organic solvent. Specific non-limiting examples of organic solvents are alcohols (eg ethyl alcohol, glycerin), ethers (eg diethyl ether), esters (eg ethyl acetate, butyl acetate), ketones (eg acetone), hydrocarbons (eg hexane, heptane) ...

The term "lithography" used to describe the present invention refers to a set of physicochemical processes for the formation on a substrate of structures consisting of micro- or nano-electronic and / or optical components.

Resolution is an important parameter of the lithography process. It is determined by the number of lines of equal thickness that can be obtained without merging on 1 mm of the substrate surface.

Contrast (contrast) is also an important parameter of the lithography process. This parameter characterizes the ability to obtain a sharply differentiated boundary between the exposed and unexposed areas of the resist, i.e. characterizes the profile of the formed resist mask, and is directly related to the resolution of the resist: the higher the contrast, the higher the resolution. The contrast is determined by a curve that characterizes the dependence of the normalized residual thickness of the resist in the developed area (normalized to the initial thickness of the resist) on the logarithm of the dose. Contrast γ is the tangent of the slope of the tangent to the given curve.

The term "resist" used to describe the present invention, in the field of micro- and nanoelectronics, refers to a coating used as protection during subsequent operations in the formation of a structure during lithography. The resist material must be sensitive, for example, photosensitive, to the effects of any radiation (for example, optical, X-ray, ion or electron flux), which manifests itself in a change in its physicochemical properties, for example, solubility, under the influence of this radiation.

An important characteristic of a resist is sensitivity, which is the minimum dose of radiation that must be transmitted to a resist site in order for its full development (complete removal of the exposed resist) to become possible within a reasonable time (usually 5-10 min).

The term "exposure" as used to describe the present invention refers to the effect of radiation or flux of elementary particles, in particular, electrons, on the resist material.

The term "developing" as used to describe the present invention refers to the treatment of an exposed resist with a solvent capable of dissolving and removing the resist material from the exposed areas.

The term "mask" used to describe the present invention refers to a relief structure that is formed on the surface of a substrate from a resist layer after it has been exposed and developed. Typically, the mask is a resist layer with holes of a certain shape. The shape and size of the holes determine the shape of the elements of micro- or nano-electronic or optical components that will be formed on the surface of the substrate during the lithography process.

The term "lift-off", also used in reverse lithography to describe the present invention, refers to a method of forming micro- or nano-electronic or optical components on the surface of a substrate, in which a mask is formed on the surface of the substrate having holes (by depositing a resist film, exposing certain areas of the film to radiation and then developing to obtain a mask), a layer of a substance (usually a metal) is applied over the mask, from which it is necessary to form micro- or nano-electronic or optical components, after which the mask is removed, while on the surface of the substrate in those places where the mask holes were, the applied substance remains in the form of a relief structure, and the substance that was located in those places where the mask had no holes, i.e. on the surface of the unexposed resist is removed together with the mask (the so-called "explosion"). Thus, the mask defines the shape of the resulting relief structure. In general, accurate removal of the resist requires that the resist film be two or more times thicker than the layer of the applied substance, and also that the walls of the resist have a negative slope, which excludes the possibility of their coating with the applied material. This process is an alternative to etching, therefore it is used for materials that are difficult to etch.

The term "etching" as used to describe the present invention refers to the step in the lithographic process that removes a portion of the substrate material from areas not protected by the resist mask, i.e. where the mask has holes. Etching can be liquid (liquid) and dry. By liquid etching is meant treatment with a liquid capable of dissolving the substrate material, wherein dry etching is the treatment of the substrate with a plasma excited by a high-frequency electric field. Dry etching includes, but is not limited to, etching with oxygen-containing plasma, halogen-containing plasma (in particular, chlorine and / or fluorine-containing plasma), and ion beam etching.

The term "doping" as used to describe the present invention refers to the incorporation of small amounts of material into a substrate in order to control its properties.

The methods of the present invention can be carried out using known equipment. Non-limiting examples will be given below.

In one embodiment of the present invention, polysaccharide compounds are used as the photosensitive resist. However, the present invention is in principle not limited to polysaccharide compounds only. Without wishing to be limited by a specific theory, the authors of the present invention believe that any high molecular weight material with the following combination of properties can be used as a resist in the present invention: a decrease in the average molecular weight when exposed to electromagnetic radiation (including a flux of elementary particles), an increase in solubility with a decrease in the average molecular weight and the ability to form chelate complexes with transition elements.

The deposition of a polysaccharide compound resist film onto a substrate can be accomplished by methods known in the art. For example, a solution of a polysaccharide compound of a suitable concentration in a suitable solvent is prepared, applied to a support, and then dried. In an illustrative embodiment, a solution of the polysaccharide compound is prepared in water, another inorganic or organic solvent. The solvent for preparing the solution of the polysaccharide compound is selected so that it dissolves the polysaccharide compound. In a specific illustrative embodiment of the present invention, the concentration of the polysaccharide compound solution to be applied to a support is 1 to 10%, depending on the molecular weight of the polysaccharide compound and the polysaccharide compound cation. Without wishing to be bound by a particular theory, the inventors believe that the lower the molecular weight of the polysaccharide compound, the higher the concentration of the solution to be applied to the support must be in order to achieve sufficient viscosity. For each specific molecular weight polysaccharide compound, the concentration of the solution must be adjusted to provide the proper film thickness under the specified application rotation conditions and substrate size. In one illustrative embodiment, the application of the film of the polysaccharide compound to the substrate is carried out using a rotary deposition technique to provide a uniform film of a certain thickness. In a specific illustrative embodiment, the application of the polysaccharide compound film is performed by centrifugal force. In one particular embodiment, the application of the polysaccharide compound film is performed by centrifugation. In a more specific embodiment, the application of the film of the polysaccharide compound is carried out using a spincoater.

In one optional embodiment of the present invention, the polysaccharide compound solution is further purified prior to application using known techniques. In one illustrative embodiment, the polysaccharide compound solution is further centrifuged prior to application. In another illustrative embodiment, the polysaccharide compound solution is further filtered prior to application.

In one illustrative embodiment, the polysaccharide compound is dried after the film is applied to the substrate. In a specific embodiment, after the polysaccharide compound film is applied to the substrate, it is dried in a stream of air.

In one optional embodiment, after application of the film, prior to exposure, additional processing is performed on the substrate coated with the film. In one illustrative embodiment, the film-coated substrate is heat treated. In one specific illustrative embodiment, the film-coated substrate is heated. In another specific illustrative embodiment, the film-coated substrate is cooled. In a specific embodiment, the film-coated substrate is heated to a temperature above the glass transition temperature of the polysaccharide compound. In another exemplary embodiment, the film-coated substrate is treated with a solution containing at least one transition element, in particular a salt of the transition element. In a particular embodiment, treating the film-coated substrate with a solution containing at least one transition element allows the developed film to be easily removed from the substrate and transferred to another surface. In another illustrative embodiment, the film-coated substrate is treated with at least one organic or inorganic substance. In one specific embodiment, the organic material is an organic solvent. In a more specific embodiment, the organic material is an alcohol. In an even more specific embodiment, the alcohol is a polyhydric alcohol. In an even more specific embodiment, the organic material is glycerin. In another specific embodiment, the inorganic material is a salt, in particular a carbonate salt. In another specific embodiment, the inorganic material is an alkali metal salt. In an even more specific embodiment, the inorganic material is an alkali metal carbonate, in particular sodium carbonate.

In one embodiment, the polysaccharide compound film is exposed. In a particular embodiment, predetermined regions (regions) of the polysaccharide compound film are exposed. As a result of exposure of the polysaccharide compound, the molecular weight of the polymer chains (depolymerization) decreases, as a result of which the solubility of the polysaccharide compound increases. The exposure of the film of the polysaccharide compound is carried out by known methods. In one illustrative embodiment, the exposure of the polysaccharide compound film is performed with a stream of elementary particles. In a specific illustrative embodiment, the particle stream is an electron stream (electron beam). In one illustrative embodiment, the electron flow is provided using an electron microscope. In one illustrative embodiment, the electron flow is provided by an electron beam (electron) lithography system.

In another illustrative embodiment of the present invention, the exposure of the polysaccharide compound film is performed by electromagnetic radiation. In a specific illustrative embodiment, the electromagnetic radiation is ultraviolet (UV) radiation. In one specific illustrative embodiment, the UV radiation is "deep" UV radiation (deep ultra violet (DUV)) with a wavelength of 248 nm. In an illustrative embodiment, "deep" UV radiation is provided by a laser. In a specific embodiment, the laser is a Kr / F (248 nm) excimer laser. In another specific illustrative embodiment, UV radiation is "extreme" UV radiation (extreme ultraviolet E-UV (English extreme ultra violet - EUV)) with a wavelength of 10-121 nm. In a more specific embodiment, the exposure is performed with extreme UV radiation at a wavelength of about 13.5 nm. In another particular illustrative embodiment, electromagnetic radiation includes x-rays with a wavelength of 10 ^-3 -10 nm. In another specific illustrative embodiment, the electromagnetic radiation is gamma radiation with a wavelength of less than 10 ^-3 nm.

Without wishing to be bound by a particular theory, the present inventors believe that upon exposure, the destruction of the polymer chains of the polysaccharide compound in the resist film occurs to obtain oligomers having a lower molecular weight and, accordingly, higher solubility compared to the parent polysaccharide compound.

In one embodiment, after exposure, the film is contacted with a transition element solution to develop the exposed portions of the film. In a particular embodiment, the development of the exposed portions of the film is carried out with a solution of the transition element salt to obtain a resist mask on the surface of the substrate. The preparation of the salt solution of the transition element is carried out by known methods. In an illustrative embodiment, a solution of a salt of a transition element of a certain concentration is prepared, the pH of the solution is determined, and, if necessary, the pH is adjusted to the required value using appropriate methods. Without wishing to be bound by a particular theory, the inventors of the present invention believe that the transition element ions present in the developer solution are reactive and interact with the polysaccharide compound film to form a chelate complex. Such a chelate complex is insoluble in water and organic solvents, since the protonated groups of the polysaccharide molecule are occupied by ions of transition elements. The development of the exposed resist as a whole is based on a balance between two conflicting processes: dissolution of the polymer (polysaccharide compound) and the formation of an insoluble complex of the polysaccharide compound with transition element ions. Both processes depend on the average molecular weight of the polysaccharide compound, which can be locally altered by exposure to electromagnetic radiation (including exposure to electron flux). Due to the fact that as a result of exposure of the polysaccharide compound there is a decrease in the molecular weight of the polymer chains, their masses are in a range in which dissolution prevails over chelation. The unexposed film, on the contrary, primarily interacts with the ions of the transition element, due to which it becomes insoluble. Thus, the transition element solution acts as a dissolution inhibitor.

In other words, when the resist based on the polysaccharide compound is exposed in the exposed areas of the resist, the destruction of the polymer chains of the polysaccharide compound occurs, leading to a decrease in the average molecular weight of the polymer chains, as a result of which the treatment of the resist with a developer solution leads to the dissolution of the resist material only in the exposed areas, and the unexposed film polysaccharide compound does not dissolve. The authors of the present invention believe that the lack of dissolution of the unexposed resist is due to the fact that the ions of the transition elements in the developer solution chelate the polymer chains of the polysaccharide compounds, as a result of which, when the film is treated with the developer solution, the stabilization of the unexposed film of the polysaccharide compounds is observed and the rate of its dissolution decreases.

To implement the method, it is necessary that when the resist material is exposed, its average molecular weight decreases, i.e. the process of destruction of polymer chains of the resist material prevailed over the process of crosslinking of the polymer chains of the resist material with each other, and, in addition, the resist material should be characterized by an increase in solubility with a decrease in molecular weight. Also, the resist material must be capable of chelating with transition element ions. Accordingly, for the purposes of the present invention, a high molecular weight material is suitable as a resist having the specified combination of properties: a decrease in molecular weight upon exposure, an increase in solubility with a decrease in molecular weight, and the ability to form a chelate complex with ions of transition elements. The polysaccharide compounds used in the present invention exhibit this combination of properties. The authors of the present invention believe that the ability of polysaccharide compounds to form chelate complexes with transition metal ions is due to the presence in the molecules of polysaccharide compounds of free functional groups, in particular amino groups, hydroxyl, carboxyl groups.

The profile of the developed exposed area can be characterized by the following parameters: the average residual thickness of the exposed resist area relative to the average residual thickness of the unexposed resist area, the shape of the exposed area after development, in particular the angle of inclination of the wall relative to the substrate.

In one illustrative embodiment, the transition element salt solution is hot (heated), i. E. has a temperature higher than the ambient temperature, or cold (chilled), i.e. has a temperature below the ambient temperature. In one illustrative embodiment, the use of a cold transition element salt solution to develop the exposed resist provides improved resolution of the method of the present invention. In another illustrative embodiment, the use of a hot junction salt solution to develop the exposed resist provides an increase in the reaction rate.

In one embodiment, after development, the substrate is treated with a resist mask applied thereto. The processing of the substrate with the resist mask applied to it is carried out by known methods. In one exemplary embodiment, the resist mask applied to the substrate is etched to remove the surface layer of the substrate to a specific depth. In a specific embodiment, the etching is a liquid etching. In a more specific embodiment, liquid etching is the treatment of a substrate with a liquid. In another specific embodiment, the etching is dry etching. In a more specific embodiment, dry etching is ionic (ion-plasma) etching. In a more specific embodiment, dry etching is plasma treatment of the substrate.

In another illustrative embodiment, the treatment of a substrate with a resist mask applied thereto is performed by depositing a material onto a substrate with a resist mask applied thereto. In a specific embodiment, the deposition is metal sputtering. In a more specific embodiment, the deposition is vacuum deposition.

In another illustrative embodiment, the resist mask applied to the substrate is doped. In another illustrative embodiment, the resist mask applied to the substrate is treated by any combination of these treatments.

In one embodiment, the mask is removed from the surface of the substrate to produce an embossed pattern (image) on the substrate. Removing the mask from the surface of the substrate to obtain a relief pattern on the substrate is carried out by known methods. In one illustrative embodiment, removal of the mask from the surface of the substrate is performed by treatment with water. In another illustrative embodiment, removal of the mask from the surface of the substrate is performed by treatment with a solution that does not contain transition elements. In a specific embodiment, the solution free of transition elements is an acid solution. In a more specific embodiment, the acid solution is a weak acid solution. In an even more specific embodiment, the acid solution is a formic acid solution. In an even more specific embodiment, the acid solution has a concentration of 0.01 to 0.1 wt%. or from 0.01 to 0.1% vol. In another specific embodiment, the transition-free solution is a non-transition salt solution. In a more specific embodiment, the solution free of transition elements is sodium carbonate solution, preferably at a concentration of 100 mM. When the resist mask is removed with an acid solution, the chelate complex of the polysaccharide compound with transition element ions is destroyed due to low pH values (acidic environment), which leads to the dissolution of the resist film. When the resist mask is removed with water, the ions of the transition elements are diffused into the water, as a result of which the chelate complex of the polysaccharide compound is destroyed, and the film of the polysaccharide compound is dissolved. The specified processing of the substrate with the mask applied to it makes it possible to ensure quick and complete removal of the resist mask from the surface of the substrate to obtain a relief pattern on the substrate of high resolution.

One of the non-limiting examples of a combination of conditions under which it is possible to simultaneously obtain high contrast, complete removal of exposed areas and minimal removal of unexposed areas, as well as provide the possibility of explosive lithography, is the following set of stages:

- bringing the chitosan compound film into contact with about 400 mM aqueous solution of NiCl ₂ for about 5 minutes at a pH of about 5.5;

- bringing the chitosan compound film into contact with about 400 mM NiSO ₄ aqueous solution for about 5 minutes at a pH of about 5.5;

- rinsing with water for about 30 seconds.

In general, based on the patterns described here, a person skilled in the art will be able to select suitable conditions for carrying out the proposed methods, depending on the task at hand.

The following are examples of implementation of the present invention. The present invention is not limited to the presented examples.

Examples of

General methodology

Getting the film

The polysaccharide compound was dissolved in deionized water or MQ water to obtain a solution of a certain concentration (from 1 to 10%, depending on the molecular weight of the polysaccharide and the cation of the polysaccharide compound: the lower the molecular weight, the higher the concentration of the solution must be to achieve sufficient viscosity). For each specific polysaccharide compound of a specific molecular weight, it is necessary to select the concentration of the solution to ensure the proper film thickness under the specified rotation conditions and substrate size. Then the resulting solution was applied to a 5 mm thick silica substrate using a spincoater at a rotation speed of 3500 rpm with an acceleration of 3500 rpm / (min * s) to obtain a film of a polysaccharide compound of a certain thickness. In some cases, the film deposition solution was additionally filtered before being applied to the substrate to remove impurities: by centrifugation at 13,200 rpm (15,000 g) for 10 min, centrifugation in a test tube with a 100 nm filter, or filtration through a 200 nm syringe filter. It has been found that storing the solution for several months prior to film application does not affect the properties of the resist, but only changes the viscosity of the solution, which can result in an improper film thickness. Dry film aging, on the other hand, can significantly affect development and explosive lithography.

Exposure

Next, the substrate with the applied film was exposed to an electron flow or electromagnetic radiation. Electron beam exposure was performed using an electron lithography system. The accelerating voltage was kept constant at 50 kV. The beam currents were in the range of 50 pA to 10 nA, which, in combination with a change in the irradiation time, made it possible to provide exposure doses in the range from 20 to 15000 C / cm ² . Exposure to electromagnetic radiation in the ultraviolet range (deep ultraviolet) was performed using a Kr / F (248 nm) krypton-fluorine femtosecond laser operating at an energy density of 20 mJ / cm ² .

Manifestation.

After exposure, the film was developed in Petri dishes mounted on an orbital shaker operating at 200 rpm. All tests were carried out at 22 ° C.

Metal deposition.

The deposition was carried out by vacuum deposition of a titanium Ti layer 1 nm thick (bottom layer) and a palladium Pd layer 11 nm thick (top layer) on a substrate with a resist mask applied.

Removal of unexposed film and explosive lithography

The unexposed resist film was removed with a highly diluted solution (with a concentration of 0.1%) of formic acid, deionized water, or a solution of sodium carbonate Na ₂ CO ₃ with a concentration of 100 mM. It should be noted that changing the ionic aqueous medium significantly affects the development process, and, therefore, the developer solution should be prepared immediately before development.

Microscopy

A Leica optical microscope was used to characterize the steps of the described method. To analyze the morphology, thickness, shape of the exposed areas, bottom cleanliness, and mechanical properties of the film after various types of treatment, a Bruker Multimode V8 atomic force microscope was used in the Scan-Asist-Air and PeakForce-HR modes. Used soft tips with a stiffness constant k = 0.4 N / m.

Some of the tests carried out in accordance with the above procedure are described in more detail below.

Example 1

A solution of 165 kDa chitosan formate in water was prepared, applied to a substrate in the form of a film, and the film was exposed to UV radiation according to a specific pattern. The development was carried out in two stages: first with an aqueous solution of NiCl ₂ (400 mM, pH 5.5, 5 min), then with an aqueous solution of Ni ₂ SO ₄ (400 mM, pH 5.5, 5 min). After development, water was washed for 30 seconds and metal was sprayed. The unexposed film was removed with a 0.1% formic acid solution. A photograph of the formed image on a substrate obtained with an optical microscope is shown in FIG. 1 (b).

Example 2

Analogously to example 1, in which, instead of 165 kDa chitosan formate, 65 kDa chitosan acetate was used and the exposure was performed with an electron flow. A photograph of the structure on a substrate obtained with an optical microscope is shown in FIG. 1 (b).

Example 3

Analogously to example 2, in which the development was carried out with a solution of NiCl ₂ 400 mM with different pH (5.0, 5.5, 6.0, 6.5, 7.0, 7.5) for 10 minutes. Dose tests for each pH are shown in FIG. 9, and the data obtained from the analysis of these tests are plotted in FIG. 2 (b). The graph shows that when the pH of the developer solution is less than 5, the dissolution of the exposed and unexposed resist is observed even at a very small exposure dose, which is due to the release of ions of the transition element chelating the polysaccharide compound from the unexposed film, which leads to the dissolution of the unexposed resist. At a pH greater than 7.5 under the test conditions, dissolution of the exposed resist stops. As can be seen from the graph, at pH 6.5 or more, to ensure its full development in a reasonable time, higher radiation doses are required during exposure than at a lower pH.

Example 4

Analogously to example 2, in which the development was carried out for 5 minutes with an aqueous solution of NiCl ₂ with pH 5.5 with different concentrations: 5, 10, 25, 60, 90, 200, 500, 900, 5000 and 9000 mM. This example is illustrated by the graph in FIG. 2 (d). The graph shows that with an increase in the concentration of the transition element in the developer solution, the contrast of the resist increases. To ensure complete removal of the resist material from the exposed area and the absence of dissolution of the resist material in the unexposed area, the resist contrast should be 0.6 or more. As can be seen from the graph, such contrast values are provided at a developer solution concentration of 60 mM or more.

Example 5

Analogously to example 2, in which chitosan acetate 700 kDa was used. Optical photographs of the structures on the substrate obtained as a result of explosive lithography are shown in FIG. 3 (a) and 3 (c). FIG. 3 (a) shows the structures obtained in the dose test, in which the exposure dose increases from the lower left corner to the upper right corner, while the dose changes slowly along the vertical, and quickly along the horizontal. It can be seen that when the dose was changed, almost the same results were obtained. FIG. 3 (c) shows the minimum dimensions of the elements on the substrate that can be obtained under the specified process conditions.

Example 6

Similarly to example 2, in which chitosan acetate 700 kDa was used, the development was carried out with a solution of nickel chloride with a concentration of 2500 mm. The resulting explosive lithography structures are shown in FIG. 3 (b). It can be seen that when the solution of the high concentration transition element is developed, it is possible to achieve a high resolution of the image formed on the substrate.

Example 7

Analogously to example 2, in which chitosan acetate 700 kDa was used and films with a thickness of 90 and 200 nm were applied. Optical photographs of structures obtained on a substrate as a result of explosive lithography in a dose test are shown in Fig. 4. It can be seen that at a film thickness of 200 nm, the edges of the image on the substrate are uneven and indistinct.

Example 8

Analogously to example 2, in which chitosan acetate of different molecular weights was used for film deposition: 20, 65, 165, 200, and 700 kDa. For each molecular weight, a standard dose test was performed with a change in the exposure dose in the low (25-750 μC / cm ² , current 50 pA) and high (500-15000 μC / cm ² , current 10 nA) ranges. The data obtained are shown in FIG. 5. As can be seen, the molecular weight of the polysaccharide compound practically does not affect the properties of the polysaccharide compound as a resist.

Example 9

Analogously to example 2, in which films of different chitosan compounds of the same molecular weight of 165 kDa were applied: acetate, formate, glycolate, lactate, chitosan succinate, and carboxymethylchitosan. The data obtained are shown in FIG. 6. It can be seen that all the studied compounds of chitosan make it possible to provide a homogeneous film and complete removal of the exposed resist as a result of the development and absence of dissolution of the unexposed one. In the case of formate, it takes a longer time to prepare the solution. In the case of chitosan succinate and carboxymethylchitosan, a rather rapid dissolution of the film in water is observed even after chelation; therefore, it is necessary to adjust the time of washing with water after development.

Example 9

A solution of 65 kDa chitosan acetate in water was prepared and applied to a substrate in the form of films. A study was made of the effect of the purity of the polysaccharide compound solution on the morphology of the resulting films. In the first case, the solution was not subjected to additional purification before application; in the second case, the solution was centrifuged at 13200 rpm (15000 g) for 10 min before application, in the third case, it was centrifuged in a test tube with a filter with a pore diameter of 100 nm, and in the fourth case. the case was filtered through a 200 nm syringe filter. Photographs of films obtained from these solutions are shown in FIG. 7. As can be seen, the chitosan acetate film obtained from the solution filtered through a syringe filter with a pore diameter of 200 nm is characterized by the highest homogeneity and the minimum number of defects. Accordingly, the removal of impurities up to 200 nm in size from the solution of the chitosan compound prior to its deposition on the substrate makes it possible to obtain a more uniform film than without additional purification.

Example 10

Similarly to example 2, in which chitosan acetate 700 kDa was used, a metal with a thickness of 20 nm was sprayed and the following solutions of salts of transition elements with the same concentration of 400 mM and pH 5.5 were used as developers: chloride, nitrate, acetate, sulfate and formate of nickel, copper sulfate , cobalt acetate alone or in combination with a surfactant (Triton X-100), Mohr's salt. Development was carried out for 5 minutes. The results are shown in FIG. 8. It can be seen that only with nickel formate it was not possible to achieve complete removal of the resist from the exposed region under the indicated conditions, while the use of solutions of the remaining salts of transition elements for the development of solutions made it possible to selectively remove the exposed resist in the absence of dissolution of the unexposed one, followed by obtaining an image on a substrate with a high resolution. However, in the case of development with a solution of nickel formate, it is possible to select such conditions that can provide a clear pattern on the substrate after removing all the resist.

Example 11

Similarly to example 2, in which chitosan acetate 700 kDa was used and after development (a) washing was not performed, (b) washed with water for 30 seconds, (c) washed with water for 10 minutes. The data obtained are shown in FIG. 10. As can be seen, in the case of prolonged washing with water (10 min) after development, a large deviation of the developed structure from the exposed template is observed, since the unexposed resist ions of transition elements chelating the molecules of polysaccharide compounds are washed out from the film, and, accordingly, the unexposed regions dissolve.

Example 12

Similar to example 2, in which the development was carried out (a) with a solution of nickel chloride 5 mM and pH 5.5 for 5 min, (b) 2500 mM and pH 5.5 for 5 min, (c) only a solution of nickel chloride 400 mM for 10 min or (d) successively with a solution of nickel chloride 400 mM and pH 5.5 for 5 min and a solution of nickel sulfate 400 mM for 5 min. The data obtained are shown in FIG. 11, from which it can be seen that an increase in the concentration of the transition element ion in the composition of the developer solution (from 5 mM in the graph (a) to 2500 mM in the graph (b)) and the change in the anion in the developer solution (only chloride ion in the graph (c) and the combination of chloride ion and sulfate ion in plot (d)) results in an increase in resist contrast.

Example 13

Analogously to example 2, in which chitosan succinate 165 kDa was used and the unexposed film was removed with water. Complete removal of the resist was observed within 1 min to obtain a high resolution structure on the substrate.

Example 14

Analogously to example 2, in which carboxymethylchitosan was used and the unexposed film was removed with water. Complete removal of the resist was observed within 1 min to obtain a high resolution structure on the substrate.

Claims (55)

1. A method of developing exposed areas of a film of chitosan, its salt or its derivative deposited on a substrate, including: bringing a film of chitosan, its salt or its derivative, which was applied to the substrate and exposed, into contact with a solution containing at least one transition element. 2. A method according to claim 1, wherein the exposed areas are areas of the film irradiated with a particle flux, preferably an electron flux, and / or electromagnetic radiation, preferably deep UV radiation, extreme UV radiation, gamma radiation or X-rays. 3. A method according to claim 1 or 2, wherein the film has a thickness of 20 to 190 nm, preferably 50 to 160 nm, more preferably 90 to 150 nm. 4. A method according to any one of claims. 1-3, in which the chitosan derivative is its amino derivative, nitro derivative, sulfo derivative, halogen derivative, phosphoric acid derivative, ether, ester. 5. A method according to any of the preceding claims, wherein the chitosan is beelosan. 6. The method of claim 1, wherein the salt is a salt of a monobasic, dibasic, tribasic, or tetrabasic acid. 7. A process according to claim 1, wherein the salt is a salt of an organic acid, in particular a salt of a carboxylic acid, in particular a salt of formic, acetic or propionic acid, or mixtures thereof. 8. The method of claim 1, wherein the chitosan salt or other chitosan derivative is selected from the group consisting of acetate, formate, lactate, glycolate, succinate, chloride, chitosan citrate, phthaloylchitosan, and carboxymethylchitosan. 9. A method according to any of the preceding claims, wherein the transition element is a d-element or an f-element. 10. A method according to any one of the preceding claims, wherein the transition element is a fourth period transition element, a fifth period transition element, a sixth period transition element, or a seventh period transition element. 11. A method according to any of the preceding claims, wherein the transition element is selected from the group consisting of zinc, nickel, copper, cobalt, iron. 12. A method according to any one of the preceding claims, wherein the solution containing the at least one transition element is a salt solution of the at least one transition element. 13. The method of claim 12, wherein the salt of the at least one transition element is selected from the group consisting of an inorganic acid salt and an organic acid salt. 14. A process according to claim 12 or 13, wherein the salt of at least one transition element is selected from the group consisting of chloride, nitrate, sulfate, formate, acetate, Mohr's salt (ammonium-iron (II) sulfate). 15. A method according to any of the preceding claims, wherein the concentration of the at least one transition element in the solution is at least 1 mM, preferably at least 20 mM, more preferably at least 200 mM. 16. A method according to any one of the preceding claims, wherein the solution containing the at least one transition element has a pH of 4 to 7.5, preferably about 5.5. 17. A method according to any of the preceding claims, wherein the solution containing at least one transition element further comprises organic substances, in particular solvents, polymers, surfactants. 18. A method according to any one of the preceding claims, wherein contacting the film with a solution containing at least one transition element is carried out for a period of 10 seconds to 60 minutes, preferably 5 to 10 minutes, most preferably about 5 minutes ... 19. A method according to any one of the preceding claims, further comprising the step of bringing the film into contact with a second solution comprising at least one second transition element other than the first. 20. The method of claim 19, which comprises sequentially bringing the chitosan film into contact with a nickel chloride solution and a nickel sulfate solution. 21. A method according to any of the preceding claims, further comprising the step of washing the film. 22. The method of claim 21, wherein the washing step is performed for a period of 10 to 60 seconds. 23. A method according to any of the preceding claims, further comprising a drying step. 24. A method according to any of the preceding claims, wherein the support is or contains carbon nanotubes, organic semiconductors, protein, lipid structures, DNA, biopolymer fibers, bacterial nanowires, or any combination thereof. 25. A method according to any of the preceding claims, comprising sequentially the following steps: - bringing the chitosan compound film into contact with about 400 mM NiCl2 aqueous solution for about 5 minutes at a pH of about 5.5; - bringing the chitosan compound film into contact with about 400 mM NiSO4 aqueous solution for about 5 minutes at a pH of about 5.5; - rinsing with water for about 30 seconds; - drying. 26. Use of a solution containing at least one transition element as a developer of exposed areas of a chitosan film, its salt or its derivative. 27. A method for forming at least one component on a substrate, comprising the following steps: a. applying a film of chitosan, its salt or its derivative to the substrate; b. exposure to predetermined areas of said film with a stream of elementary particles and / or electromagnetic radiation (exposure); from. development of exposed areas of the film by implementing the method according to any one of claims. 1-25 to form a masked substrate; d. processing a substrate with a mask applied to it by etching, deposition, alloying, or any combination thereof; e. removing the mask from the surface of the substrate to form at least one component on the substrate, the component being a micro- and / or nano-electronic and / or optical component. 28. The method of claim. 27, wherein the particle flux is an electron flux and / or the electromagnetic radiation is deep UV radiation, extreme UV radiation, gamma radiation, or X-rays. 29. A method according to claim 27 or 28, wherein the film has a thickness of 20 to 190 nm, preferably 50 to 160 nm, more preferably 90 to 150 nm. 30. The method according to any one of paragraphs. 27-29, in which the deposition of the film on the substrate in step a. carried out from a solution of chitosan, its salt and its derivative, which is pre-filtered or subjected to centrifugation. 31. The method according to any of paragraphs. 27-30, additionally including after stage a .: temperature treatment of the substrate, and / or treatment of the substrate with a solution containing at least one transition element, and / or treatment of the substrate with at least one inorganic or organic substance. 32. The method of claim 31, wherein the organic matter is glycerin. 33. The method according to any of paragraphs. 27-32, in which the etching is liquid etching or dry etching. 34. The method according to any of paragraphs. 27-33, in which the removal of the mask from the surface of the substrate is carried out by exposure to water or a solution, preferably a solution containing no transition elements, preferably an aqueous solution. 35. The method of claim 34, wherein the solution free of transition elements is a solution of an acid or salt other than a salt of the transition element. 36. The method according to p. 35, in which the acid solution has a concentration from 0.01 to 0.1% of the mass. 37. The method according to any of paragraphs. 35, 36, in which the acid is a monobasic, dibasic, tribasic, or tetrabasic acid. 38. The method according to any of paragraphs. 35-37, in which the acid is an organic acid, in particular a carboxylic acid, in particular formic, acetic, propionic acid, or mixtures thereof. 39. The method according to any one of paragraphs. 35-38, in which the acid is a weak acid. 40. The method according to any one of paragraphs. 35-39, in which the acid is formic acid. 41. A method according to claim 34 or 35, wherein the solution free of transition elements is an alkali metal carbonate solution, preferably with a concentration in the range of 50 to 150 mM. 42. The method according to any of paragraphs. 27-41, which is a lithography method, in particular an explosive (reverse) lithography method. 43. The method according to any of paragraphs. 27-42, the steps of which are performed more than once to obtain a structure containing more than one layer of components. 44. The method according to any of paragraphs. 27-43, in which the substrate coated with at least one component is an integrated circuit.

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