RU2204179C1 - Method for shaping nanotopography on film surface - Google Patents

Abstract

FIELD: microelectronics engineering. SUBSTANCE: method involves covering film surface with silicon layer whose thickness equals one and a half to three depths of nanostructure formation in silicon layer; spraying silicon surface with stream of nitrogen molecule ions in vacuum, nitrogen ion energy, nitrogen ion angle of flow relative to silicon surface, depth of nanostructure formation and nanostructure height being chosen basing on nanostructure wavelength ranging between 30 and 180 nm before formation of nanostructure spaced apart from film at one third of wavelength on nanostructure wave valleys with wave crest positioned perpendicular to projection of ion flow on silicon surface; transferring nanostructure topography to film surface with nanostructure and film materials being removed by ion-beam or plasma etching. EFFECT: improved formation of nanotopography on film surface. 9 cl, 16 dwg

Description

 The invention relates to non-lithographic methods of forming a wave-like nanorelief on the surface of films. Films transparent to optical radiation with such a nanorelief can be used to orient liquid crystals in liquid crystal (LCD) devices, in particular, LCD indicators (LCD) and LCD screens (LCD), for the manufacture of polaroids and phase-shifting, antireflection, antireflection, anti-glare and scattering films in optical devices. Films with a nanorelief and with an additional reflective coating on their surface can be used as directional diffuse reflectors, in particular in LCDs and LCDs of a reflective type. Films of silicon and amorphous diamond with a nanorelief can also be used as electron emitters (cold cathodes with field emission of electrons) in vacuum and solid state electronics devices, in particular in electroluminescent lamps, including LCD and flat screens.

 More specifically, the invention relates to non-lithographic methods of forming a relief using the ion beam technique and dry plasma processes used in microelectronics technology, namely, to the self-formation of a wave-like nanorelief on the surface of an amorphous silicon layer deposited on a film by irradiating this layer with a stream of nitrogen ions and transferring the nanorelief into located below the layer or film by ion beam or plasma etching of materials of amorphous silicon and film. In this case, in particular, the nanorelief can be modified using a selective and anisotropic plasma process until the formation of amorphous silicon nanobands on the underlying film, followed by the use of an anisotropic plasma process using amorphous silicon strips as a mask until the nanorelief is formed in the underlying film.

 Currently, LCDs and LCDs are widely used to display graphic information. For the operation of various types of LCDs and LCDs, it is necessary to ensure a certain orientation of the liquid crystal molecules (for example, nematic) on the surfaces of the orienting films between which the LC layer is located.

 It is known that polymer films are used as orienting films, in particular polyimide, subjected to special machining, the essence of which is rubbing the film surface in one direction with a roller coated with a fabric with a pile of short polymer fibers (for example, viscose, polyesters, nylon etc.). An example of a mechanical method for forming an orienting polyimide film is disclosed, in particular, in the patent description (US 6219123, 04.17.2001).

 The formation of static electric charges, dust particles and the inability to strictly maintain a given direction of the fibers are the disadvantages of the mechanical method of rubbing orienting films with polymer fibers. It should be noted that this method of forming an orientation film is not compatible with the cleanliness conditions of technological rooms in which other LCD and LCD production processes are carried out.

 Known methods for the formation of orienting, polaroid and phase-shifting films based on the creation of a wave-like microrelief on their surface. Numerous examples of the formation of orienting, polaroid and phase-shifting films based on the microrelief are disclosed in the patent description in applications to LCD and LCD devices (DE 4213802, 01/21/93).

 These microreliefs are obtained as a result of applying the following methods: holographic exposure of the photosensitive polyimide layer, lithography methods known in microtechnology, microstamp technology, or the application of microstrikes on the surface of epoxy resins with a diamond-needle grinder. The disadvantages of all these methods are their high cost, low yield and low productivity. It should be noted that the cost of lithography methods increases tremendously with a line width of 100 nm or less and the use of such equipment is hardly justified for creating a simple pattern consisting of an array of lines, provided that there are non-lithographic methods for forming such a pattern.

 Known methods for forming orienting films for liquid crystals, developed by IBM specialists, are based on irradiating the surface of the film with low-energy argon ions (from 20 to 700 eV) (US 5770826, 06.23.2000; US 6020946, 1.02.2000; US 6061114, 9.05. 2000; US 6061115, 05/05/2000; US 6124914, 09/26/2000; US 6331381, 12/18/2001). However, ion irradiation in these methods does not lead to the formation of anisotropic topography on the surface of the films. Orientation is carried out by creating the preferred orientation of chemical bonds on the surface irradiated with ions. In addition, an important orientation parameter of nematics — the initial angle of inclination of molecules relative to the plane of the orienting surface — depends on the dose of ion irradiation, the angle of incidence of ions, and their energy. Thus, a high degree of control of these parameters and ensuring their uniform distribution over the film surface are necessary.

 It is known that the orientation of liquid crystals using a relief surface opens up the possibility of creating fundamentally new LCDs with significantly reduced power consumption based on the phenomenon of bistable orientation of nematics (patent: US 20010028426, 10/11/2001 and article: GP Bryan-Brown Proceedings of the International Displays Research Conference Palm Beach, Florida, USA (2000) pp. 299-232). This article also demonstrated the possibility of using new materials for the manufacture of LCEs, in particular, instead of glass substrates, films made of polyethersulfone (PES) and polyethylene terephthalate (PET) were used, as well as transparent electrodes from a mixture of indium and tin oxides (ITO) in PES / ITO used transparent electrodes from poly-3,4-ethylenedioxythiophene (PEDOT) films in PET / PEDOT structures. The use of PES, PET, and PEDOT polymer films in technology makes it possible to fabricate flexible LCDs and LCDs entirely from plastic, and the use of PEDOT films instead of ITO allows one to prepare an orienting surface directly on the surface of the PEDOT film without an additional orienting film. Microreliefs in this work were formed on the surface of the photoresist using optical lithography methods.

 Thus, it is important to have a method for the non-lithographic formation of controlled topography on the surfaces of both polymeric and inorganic materials for their use in optics.

 Known non-lithographic method of forming a corrugated surface of polymer thin optical films, based on the separation of the phases of the LC polymer and the LCD monomer. When a liquid film consisting of a mixture of these substances is irradiated with UV light, the LC polymer phase is separated from the LC monomer phase and turns into a solid, in particular, in the form of a corrugated polymer film (Ibn-Elhaj M. & Schadt M., Nature 410 (2001 ) pp. 796-799). The period and amplitude of anisotropic polymer structures in this method depends on the thickness of the liquid film irradiated with ultraviolet radiation, the composition of the mixture, and the conditions of ultraviolet irradiation. Therefore, to ensure a given period of the structure, it is required to provide a certain thickness of the liquid film, which in some cases may be unacceptable.

 Known methods for the manufacture of cold cathodes with field emission of electrons, based on the formation of a relief on the surface of diamond or silicon films. The patent (US 2001/0052469, December 20, 2001) discloses a method for forming an emitter of porous silicon. It is known that the surface of porous silicon has a developed topography of a nanometer scale and the pointed protrusions of such a surface, concentrating the electric field, are sources of field emission of electrons. However, it is also known that porous silicon is chemically unstable and its properties degrade over time. The patent (US 6204595, March 20, 2001) discloses a method for forming an emitter based on an amorphous diamond film deposited on a silicon substrate. However, the topography for the concentration of the electric field is traditionally used the relief of the silicon substrate, formed using lithography methods. As mentioned above, in the presence of non-lithographic productive methods for creating a simple pattern consisting of an array of lines 100 nm wide or less, the use of lithographic methods for this purpose becomes unjustified.

 Thus, it is also important to have a method for the non-lithographic formation of topography on the surfaces of silicon and diamond films for use in vacuum and solid-state electronics as cold cathodes with field emission of electrons.

 Known non-lithographic method of forming a wave-like nanostructure by irradiating a silicon surface with a beam of nitrogen ions, disclosed in the patent description (US 6274007, 08/14/2001). A known method of plasma modification of a wave-like nanostructure formed in a layer of amorphous silicon deposited on a layer of silicon oxide, disclosed in the description of the application for invention (RU 2001127264/28 (029205) "A method of manufacturing a field-effect transistor with periodically doped channel"). Both of these methods are the basis of the present invention.

 The technical task of the present invention is the transfer of the relief of a nanostructure self-formed on the surface of a silicon layer by the ion-beam method, to the underlying layer or film using ion-beam or plasma etching.

 The technical result is an improvement in the method of forming a nanorelief on the surface of the films.

 This is achieved by the following set of features.

 A layer of silicon is applied to the film with a thickness of one and a half to three depths of the formation of the nanostructure in the silicon layer.

 A silicon surface is sprayed with a stream of nitrogen molecule ions in a vacuum with a choice of the energy of nitrogen ions, the angle of the flow of nitrogen ions relative to the silicon surface, the depth of formation of the nanostructure and the height of the nanostructure based on the wavelength of the nanostructure in the range from 30 to 180 nm until the formation of the nanostructure that is distant films at a distance of one third of the wavelength along the troughs of the waves of the nanostructure and with the orientation of the wave crests perpendicular to the direction of projection of the ion flux onto the silicon surface.

 The relief of the nanostructure is transferred to the surface of the film, removing the materials of the nanostructure and film.

 It is preferable to carry out the formation of an ion flux of nitrogen molecules using a Kaufman ion source.

 It is preferable to remove the nanostructure materials and films by ion beam etching.

 It is preferable to remove the nanostructure materials and films by plasma etching.

 It is preferable to remove silicon nanostructures selectively with respect to silicon nitride of the nanostructure and vertically with respect to the film surface up to the film surface.

 It is preferable to remove the film material vertically relative to the film surface and selectively with respect to the nanostructure materials.

It is preferable to carry out the removal of silicon nanostructures using reactive ion etching in a plasma of Cl ₂ -Ar.

 It is preferable to remove silicon nanostructures selectively with respect to the film material.

 It is preferable to carry out the removal of the nanostructure after removal of the film material.

The invention is illustrated by drawings, where
FIG. 1 shows a cross section of a layered structure before ion irradiation;
figure 2 shows a cross section of a layered structure in the process of forming a nanostructure;
FIG. 3 shows a cross section of a wavy nanostructure formed in a silicon layer;
FIG. 4 shows a cross section of a nanostructure after anisotropic plasma etching;
FIG. 5 shows a cross-section of a nanorelief transferred to the film by isotropic plasma etching of the structure shown in FIG. 4;
FIG. Figure 6 shows a cross-section of a film with a nanorelief transferred to the film as a result of ion-beam or non-selective plasma etching of the nanostructure;
FIG. 7 shows a cross section of a nanostructure after anisotropic plasma etching, selective with respect to the film material;
FIG. 8 shows a cross-section of a nanorelief transferred to the film by anisotropic plasma etching of the structure shown in FIG. 7;
Fig.9 shows a cross section of a polarizer made on the basis of a film with a nanorelief and an LC polymer having a dichroic dye group;
10 shows a cross section of a cell of an LCD device;
11 shows a schematic representation of a comb-shaped LC polymer;
12 shows a schematic representation of a linear LCD polymer;
FIG. 13 shows a cold cathode diode type electroluminescent vacuum lamp;
FIG. 14 shows a solid-state thin-film electroluminescent lamp;
Fig. 15 shows a solid-state thin-film electroluminescent lamp with a nanorelief on the surface of a metal cathode;
Fig.16 shows a solid-state thin-film electroluminescent lamp with a nanorelief on the surface of a silicon cathode.

 The invention is illustrated by the following example.

Example. Figure 1 shows the structure consisting of layers of glass 1, transparent electrode 2, film 3 and silicon 4. In the following, number 3 denotes any film onto which the relief of the nanostructure is transferred. In this particular case, the film 3 is a polyimide film. ITO is often used as a transparent electrode. The design of layers 1, 2 and 3 (polyimide) is used for the manufacture of LCDs and LCDs. The silicon layer 4 may be a film of amorphous silicon (a-Si) or hydrogenated amorphous silicon (a-Si: H). An a-Si: H layer with a thickness of ~ 400 nm is applied, for example, in a low-frequency discharge of silane SiH ₄ for 20 minutes in a known manner (Budaguan B.G., Sherchenkov AA, Struahilev DA, Sazonov AY, Radosel'sky A.G., Chernomordic VD, Popov AA and Metselaar JW "Amorphous Hydrogenated Silicon Films for Solar Cell Application Obtained with 55 kHz Plasma Enhanced Chemical Vapor Deposition" - Journal of the Electrochemical Society, 1998, Vol. 145, 7, pp. 2508-2512). There are at least two other known methods for the formation of layers of amorphous silicon at a substrate temperature close to room temperature. One is the deposition of silicon by evaporation of a silicon target by an electron beam in high vacuum. Another is the method of magnetron sputtering of a silicon target. A wave-like nanostructure is formed in the a-Si layer deposited by any of the above methods. The thickness of the amorphous silicon layer ~ 400 nm is determined by the choice of the wavelength of the nanostructure λ = 150 nm and the conditions of its formation.

Figure 2 shows the surface of layer 4 irradiated with a stream of 5 ions of nitrogen molecules N ₂ ⁺ . The wavelength of the nanostructure λ = 150 nm corresponds to the angle of bombardment of nitrogen ions relative to the normal to the surface of layer 4, equal to 45 ^o , the ion energy equal to 8 keV, and the depth of formation of the nanostructure D _F = 120 nm at room temperature of the sample. An ion gun mounted in a vacuum chamber was used to form an ion beam. A beam of nitrogen ions with a current of 150 nA and a diameter of ~ 10 μm was deployed in a raster measuring 100 per 100 μm ² , which covered a portion of the surface of layer 4 shown in FIG. 2. As a result, a wave-like nanostructure 6 was obtained within ~ 2 minutes. In this case, the initial level of the surface of layer 4 decreased due to the ion sputtering process.

To increase the productivity of the process of nanostructure formation, it is advisable to use a Kaufman ion source, which allows large-diameter ion beams to be obtained and with an ion energy of N ₂ ⁺ more than 1 keV gives an ion current density of more than 1 mA cm ^-2 , which practically coincides with the ion current density used ion gun per raster area of 1.5 mA • cm ^-2 . Using the Kauffman ion source, it is possible to process the entire surface of a large area substrate simultaneously in ~ 2 minutes. A vacuum installation with an ion source of Kaufman should provide the possibility of ion bombardment in the range of angles from 40 to 60 ^o relative to the normal to the surface.

Formed wave-like nanostructure is shown in figure 3. It consists of regions of amorphous silicon nitride 7 and a thin layer of amorphous silicon 8 with inclusions of nitrogen atoms and NN pairs. The hollows of the nanostructure are separated from the surface of the film 3 by a distance D equal to approximately one third of the wavelength of the nanostructure. This arrangement of the nanostructure relative to the film 3 is achieved by turning off the ion flux 5 at the calculated time at a known sputtering rate of layer 4 by the ion flux N ₂ ⁺ .

 The wave crests of the nanostructure are perpendicular to the plane of the ion bombardment, which coincides with the plane of the drawing of figure 2. Therefore, the direction of the ion flux is chosen taking into account the required orientation of the nanostructure waves on the film.

After the process of forming a wave-like nanostructure, the process of its modification is carried out, which consists in the selective and anisotropic etching of the silicon layer 4 using regions 7 of the nanostructure as a mask for etching in a reactive ion plasma of Cl ₂ , Cl ₂ -Ar or Cl ₂ -He-O ₂ . Such plasma-chemical processes of etching silicon, selective with respect to silicon nitride, are known and are used in modern silicon VLSI technology (Plasma technology in the production of VLSI: Transl. From English with acronym / Ed. By N. Ainspruck, D. Brown. - M .: Mir, 1987, 472 p.). Anisotropic etching of silicon in a plasma of the composition Cl ₂ -He-O ₂ using masks of nitride and silicon oxide is disclosed in the patent description (US 5882982, March 16, 1999). Anisotropic (vertical) etching of silicon results in the nanomask shown in FIG. 4. Etching of the polymer film 3 can be due to both the presence of oxygen in the gas mixture and physical sputtering of the polyimide film with argon or helium ions. Areas of silicon 4 coated with regions of silicon nitride 7 remain on the surface of the film 3.

In the case of high selectivity of plasma-chemical etching of silicon relative to silicon nitride, there is a need for preliminary removal of thin layers 8 of the nanostructure, for example, in an HF solution strongly diluted with НNO ₃ , before modification of the nanostructure or other non-selective method of plasma-chemical etching.

The isotropic etching process of the structure shown in FIG. 4, for example, in plasma O ₂ —CF ₄ . Non-selective isotropic removal of materials 3, 4 and 7 leads to the transfer of the nanostructure relief to the film 3, as shown in Fig. 5.

 The transfer of nanorelief from layer 4 to the underlying film 3 can be carried out using ion-beam or plasma anisotropic etching. With the non-selective removal of materials of the nanostructure 6 and the underlying film 3, a relief is obtained on the surface of the film 3, shown in Fig.6. The wavelength of the transferred relief coincides with the wavelength of the nanostructure. If the sputtering coefficient of a film of 3 ions is greater than the sputtering coefficient of amorphous silicon, then the amplitude of the transferred relief exceeds the amplitude of the nanostructure. In the case of an inverse ratio of sputtering coefficients, the amplitude of the transferred relief is less than the amplitude of the nanostructure.

 For polymer films, it may be important to eliminate the effects of accelerated ions on their surface. The polymer-damaged polymer layer can be burned, for example, in oxygen plasma.

If you want to transfer the relief of the nanostructure to the silicon oxide film 3 SiO ₂ , then the silicon layer is applied to the SiO ₂ film, for example, by gas phase epitaxy, chemical vapor deposition, or any other known method. In this case, silicon oxide is practically not etched in the plasma of the composition Сl ₂ -Не-О ₂ and plays the role of a stop layer for plasma etching of the nanostructure. As a result of such plasma etching of the nanostructure, the structure shown in FIG. 7 is obtained.

Anisotropic etching of a SiO ₂ film in a fluorine-containing plasma, for example, in CF ₄ -H ₂ or CHF ₃ plasma, using a nanomask from the modified nanostructure shown in Fig. 7, followed by removal of the nanomask in the SF ₆ -O ₂ plasma leads to the formation of a structure in SiO ₂ shown in Fig. 8.

 A process similar to the one just described can be carried out with polymer films. In this case, oxygen should not be added to the gas mixture during the modification of the nanostructure, and, on the contrary, the polymer must be etched in oxygen plasma. As a result of these processes, it is also possible to obtain the structures shown in Figs. 7 and 8.

 To transfer the nanorelief into a diamond film, a silicon layer is also applied to it by any known method. Then, the formation of the nanostructure, its plasma modification, and the transfer of the nanorelief into a diamond film in oxygen plasma are carried out in a silicon layer, similar to that described above for polymer films. The result is the diamond film shown in FIG. 5. The severity of the relief protrusions depends on the selectivity and anisotropy of the used plasma processes.

 It is seen that the transfer of the nanostructure relief can be carried out using the known methods of ion beam and plasma etching. Thus, the invention can be technically implemented.

 Industrial applicability.

 The invention can be used, including when creating devices LCD and LCD, in optical instrumentation, in vacuum and solid-state electronics.

The nanorelief transferred into polymer films, in particular into polyimide, PET and PES films, into SiO ₂ films, glass, amorphous hydrogenated silicon, and others, can be used to produce polarization and phase-shifting films and to orient liquid crystals in LCD and LCD devices, such as described in the patent (DE 4213802, 01.21.93).

 For example, in FIG. 9 shows a cross-section of a polarizer made on the basis of a film with a nanorelief 3 and a thermotropic nematic LC polymer 9, which contains a dichroic dye group, with a protective film 10 of polyimide. Make a polarizer as follows. A layer of an LC polymer having low molecular weight groups 14 shown in FIGS. 11 and 12 is applied to the nanorelief film 3. The ribbed type LC polymer, as shown in FIG. 11, can be obtained on the basis of methacrylic acid. A linear-type LC polymer, as shown in FIG. 12, can be made from polyester. The low molecular weight groups 14 in the composition of the LC polymer can be groups of a low molecular weight nematic liquid crystal and groups of dichroic dyes. The LC polymer is heated to a temperature above the transition to the nematic phase, and then cooled. Below the transition temperature into the nematic phase, the LC polymer becomes an oriented nanorelief of film 3. Together with the orientation of the LC polymer, the groups of dichroic dyes that may contain iodine are aligned. One iodine-containing dye is enough to prepare a polaroid. Otherwise, yellow, red and blue dichroic dyes are mixed to achieve the effect that gives one iodine-containing dichroic dye. Thus, a film is obtained whose polarization direction is determined by the direction of the relief on the film surface 3.

In FIG. 10 shows a cross section of an LCD cell. It consists of glass plates 1, ITO layers 2, orienting films 3A and 3B rotated 90 ^° relative to each other to provide a twisted (twist) structure of the nematic liquid crystal layer 13 between the films 3A and 3B, phase-shifting plate 11 and polarizers 12.

 In addition, the nanorelief in the films shown in FIGS. 5 and 8 can be used as an antireflection coating, because the nanorelief layer has a smoothly varying refractive index between the bulk film and air. The height of such a “coating” is equal to the amplitude of the relief in the film and can be set by the thickness of the film itself.

 Applying a reflective coating, such as aluminum, to films with a nanorelief makes it a diffuse directional reflector.

 On Fig shows a device of an electroluminescent vacuum lamp of a diode type. Such lamps are known and described, for example, in the patent (US 5926239, 07.20.1999). The lamp consists of two glass plates 1 on which the anode and cathode are located. The anode consists of an ITO 2 film on which a phosphor film 15 is deposited. A film 3 with a nanorelief serves as a cathode. A vacuum gap is formed between the films 15 and 3. The voltage source 16 is connected to the ITO 2 films and the cathode 3. As a cathode, diamond films with a nanorelief, as well as films of n-type single crystal and amorphous silicon, can be used. It is important to note that, as a cathode, one can also use a single-crystal silicon wafer with a nanorelief on its surface formed by modifying a plasma nanostructure. To increase the emission of electrons from the surface of the nanorelief on silicon, an additional film of amorphous diamond doped with nitrogen (a-D: N) can be deposited on the silicon surface. A method of forming a-D: N films is disclosed in the patent (US 6204595, 03.20.2001).

In FIG. 14 shows a solid-state thin-film electroluminescent lamp, known from the prior art (see, for example, patent US 5926239, 07.20.1999). It consists of a glass substrate 1, an ITO 2 film, a phosphor film 15, a SiO ₂ film 17, and a metal film (A1 or Al / Mg) 18. A voltage source 16 is connected to the ITO 2 films and the metal 18.

Films with a nanorelief can be used in a solid-state thin-film electroluminescent lamp. In FIG. 15 shows a device for a solid-state thin-film electroluminescent lamp with a nanorelief on the cathode surface. This lamp can be made in the following way. Films of ITO 2, phosphor 15 and SiO ₂ 19 are successively applied to the glass substrate 1 by known methods in a known manner. The nanorelief is transferred to a SiO ₂ film according to the present invention. On the surface of the SiO ₂ film with a nanorelief, an A1 or Al / Mg 20 film is applied. In the lamp shown in FIG. 15, the film 20 plays the role of a diffuse reflector and has improved emission properties, which improves lamp performance.

A solid-state thin-film electroluminescent lamp can be manufactured in another way (see Fig. 16). An n-type 21 silicon wafer is used as a substrate, on the surface of which, according to the present invention, a nanorelief is formed. Then, films of SiO ₂ 19, phosphor 15, ITO 2 and a film of passivating SiO ₂ 22 are successively applied.

Claims (9)

 1. The method of forming a nanorelief on the surface of the films, which consists in applying a layer of silicon to the film with a thickness of one and a half to three depths of the formation of the nanostructure in the silicon layer; spray the silicon surface with a stream of nitrogen molecule ions in a vacuum with a choice of the nitrogen ion energy, the angle of the nitrogen ion flux relative to the silicon surface, the depth of the formation of the nanostructure and the height of the nanostructure based on the wavelength of the nanostructure in the range from 30 to 180 nm until the formation of the nanostructure that is distant from films at a distance of one third of the wavelength along the troughs of the waves of the nanostructure and with the orientation of the wave crests perpendicular to the direction of projection of the ion flux onto the silicon surface; transfer the relief of the nanostructure to the surface of the film, removing materials of the nanostructure and film.  2. The method according to p. 1, characterized in that for the formation of a stream of ions of nitrogen molecules using an ion source of Kaufman.  3. The method according to p. 1, characterized in that the materials are removed nanostructures and films by ion beam etching.  4. The method according to p. 1, characterized in that the materials are removed nanostructures and films by plasma etching.  5. The method according to p. 1, characterized in that the silicon nanostructures are removed selectively with respect to the silicon nitride of the nanostructure and vertically relative to the film surface up to the film surface.  6. The method according to p. 4, characterized in that the film material is removed vertically relative to the film surface and selectively with respect to the nanostructure materials. 7. The method according to p. 5, characterized in that the silicon nanostructure is removed by reactive ion etching in a plasma of Cl ₂ -Ar.  8. The method according to p. 5, characterized in that the silicon nanostructures are removed selectively with respect to the film material.  9. The method according to p. 6, characterized in that the nanostructure is removed after removal of the film material.

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