PL227744B1 - Process for producing substrates with nano-coatings with a high surface area - Google Patents

Description

The subject of the invention is a method of producing nanocoated substrates with a high surface of semiconductor and / or dielectric materials. Such substrates, and in particular silicon, quartz or gallium nitride substrates containing such nanocoatings, can be used in sensors for measuring gas and liquid concentrations, in photovoltaic cells, and in various types of emission devices.

In the literature, various methods are known to obtain nanostructures of semiconductor and dielectric materials of various shapes, such as: nano-bars, nanotubes, nanowashes, etc. For example, in the publication: Ku, Se Jin: Jo, Gyeong Cheon et al. Nanotechnology 24 (2013) 085301 (8pp) the growth of titanium dioxide (TiO ₂ ) and alumina (Al ₂ O ₃ ) nanotubes is described using the atomic layer deposition (ALD) technique. In the described method, a special matrix is used, which consists of a silicon substrate on which there is a porous polymer layer (PS-b-PSSi) with holes about 53 nm in diameter and 200 nm in height. The porous polymer surface is first covered with layers of dielectrics and then, by dry etching, they are removed, leaving only nanotubes made of the above-mentioned on the surface of the substrate. materials. To obtain such nanostructures, the authors use complex and multi-stage etching and thermal heating processes. In the publication: Das, SK, Sahoo, SN, Sarangi, SN, & Sahoo, PK, Journal of Experimental Nanoscience, (ahead-of-print) 1-7 (2012), zinc oxide (ZnO) nanograms obtained by the hydrothermal method at a temperature of 90 ° C on various substrates such as Si, SiO ₂ , MgO and ITO.

From the publication of: Chih-Chiang Chen, Wei-Yun Cheng et al., CrystEngComm 12, 3664-3669 (2010) there are known zirconium dioxide (ZrO ₂ ) nanostructures made by the Chemical Vapor Deposition (CVD) method on semiconductor substrate. In the described process, the growth of structures takes place at temperatures in the range 550-1000 ° C.

He is known for his publications: Min Young Cho, Min Su Kim, Hyun Young Choi, Kwang Gug Yim, and Jae-Young Leem - Post-Annealing Effects on Properties of ZnO Nanorods Grown on Au Seed Layers - Bull. Korean Chem. Soc. 2011, Vol. 32, No. 3 way of growth of ZnO nanostructures by hydrothermal method. However, the method described there requires extremely careful preparation of the substrate (digestion with strong and toxic acids). High purity zinc nitrate and HMT (hexamethyltetramine) are used during the growth process, and the growth takes place at 130 ° C for up to 7 hours. After completion of the growth process, high-temperature annealing is also required.

The aim of the invention is to provide an inexpensive, simple and quick method of producing nanocoated substrates with a high surface area from dielectric and / or semiconductor materials.

The method according to the invention consists in that, first of all, on a substrate, preferably silicon, quartz or gallium nitride, in a hydrothermal process, a textured ZnO layer is produced, containing nanostructures, nanodots or nanowires attached to the substrate. The hydrothermal process is carried out at a temperature lower than 100 ° C, in less than 5 minutes, and the zinc precursor is zinc acetate and the oxygen precursor is water. Then, at a temperature of 20-800 ° C, by the method of atomic layer deposition (ALD), a semiconductor and / or dielectric nanocoating is deposited on the textured layer in the form of a layer of titanium dioxide, zirconium dioxide, hafnium dioxide or alumina, or in the form of a multilayer. The deposition of the layer is carried out in at least 10 ALD cycles, in which the precursor pulse times are in the range of 0.015-2 s, the metal precursor is an organic or inorganic precursor and the oxygen precursor is water, preferably deionized or ozone. Upon completion of the deposition, the textured ZnO layer beneath the nano-coating is removed, preferably by washing with water or by etching with hydrochloric acid.

The described method makes it possible to obtain substrates with nanocoatings with a developed surface from semiconductor and / or dielectric materials, it is simple and relatively short-lived. This method does not require the use of complicated multi-stage etching processes or high-temperature annealing, because the growth takes place at a temperature in the range of 20-800 ° C. In addition, these nanocoatings can be produced on a variety of substrates.

The invention will be explained in more detail on an embodiment of a silicon substrate with a titanium dioxide (TiO2) nanocoating.

The method according to the invention uses a completely new mechanism of growth of semiconductor and dielectric materials with a developed surface.

PL 227 744 B1

In an exemplary method, a matrix is first made of ZnO pillars attached to a substrate, in this case to a silicon substrate. For this purpose, a textured layer of zinc oxide (ZnO) containing nanograms is produced on a silicon substrate using a hydrothermal method. The hydrothermal method makes it possible to create nano-pillars attached to the substrate with their bases and relatively evenly distributed. Then, a nanopaint is deposited on the surface of these nano-pillars and partially on the surface of the silicon substrate (between the nano-pillars). In the example, a 10 nm thick layer of titanium dioxide (TiO _{2) was deposited.} This oxide material (TiO ₂ ) was deposited using ALD technology.

The presented method uses the atomic layer deposition (ALD) method as one of the possible methods of thin layer deposition. The ALD technique is a variation of the method of Chemical Vapor Deposition (CVD), which consists in the alternating feeding of reagents, called precursors, to a reaction chamber, in which a layer of the desired chemical is deposited on the substrate as a result of a chemical exchange reaction or synthesis. material. Flushing with an inert gas follows each injection of the precursor.

A typical material deposition cycle in an ALD process consists of four steps: first precursor feed time, rinse, second precursor feed time, and rinse. The layer thickness is determined by the number of cycles. An exemplary matrix was covered with a conformal nanometer layer of titanium dioxide as a result of the reaction of inorganic precursors (reactants). The TiO2 layer was deposited with 100 ALD cycles at a growth temperature of 100 ° C. In the process of depositing this layer, titanium chloride, TiCl ₄ , was used as the titanium precursor and deionized water as the oxygen precursor.

The growth parameters were set as follows: TiCl ₄ precursor pulse: 0.1 s; Pulse rinse with TiCl ₄ : 5 s; oxygen precursor pulse: 0.1 s; _{H 2} O pulse rinsing: 5 s. Neutral gas, nitrogen, N ₂ of high purity 99.9999% was used for rinsing between successive doses of precursors.

After the TiO2 layer was deposited, the ZnO nanograms were removed. These nano-columns were removed by rinsing in water, but it can also be etched in a hydrochloric acid solution. As a result of the method according to the invention, a titanium oxide nanocoating with a developed surface was obtained on a silicon substrate. The obtained nanocoating imitates the external shape of the nanobars and is in the form of nanotubes closed at the top, attached in places to a silicon substrate. The height and width of these nanotubes is closely related to the outer shape of the nanograms in the textured ZnO layer. The nanostructure obtained in this way can be used in subsequent growth processes, when there is a need to create a multilayer nanocoating or multilayer structures from any semiconductor or dielectric materials.

Claims (2)

1. The method of producing substrates with nanocoatings with a high surface of semiconductor and / or dielectric materials, in which a hydrothermal process is used, characterized in that first the substrates, especially silicon, quartz or gallium nitride substrates, are covered in the hydrothermal process with a textured layer of ZnO containing nano-columns, nanodots or nanowires attached to the substrate, the hydrothermal process is carried out at a temperature lower than 100 ° C for less than 5 minutes, the zinc precursor is zinc acetate, and the oxygen precursor is water, then at a temperature of 20-800 ° C C, by the atomic layer deposition (ALD) method, a nanocoating is deposited on the textured layer, preferably in the form of a titanium dioxide layer, a zirconium dioxide layer, a hafnium dioxide layer or an alumina layer, which is deposited in at least 10 ALD cycles with pulse times of the precursors are in the range of 0.015-2 s, the metal precursor is an organic or an inorganic precursor With an oxygen precursor, water, preferably deionized or ozone, is removed after the deposition is complete, the textured ZnO layer beneath the nanocoat is removed, preferably by washing with water or by etching with hydrochloric acid. 2. The method according to p. The method of claim 1, wherein the nanocoating is deposited in the form of a multilayer.