Method of production of regular systems of nano-size silicon whiskers

FIELD: technological processes.

SUBSTANCE: method of production of regular systems of nano-size silicon whiskers includes preparation of silicon plate by masking of its surface with photoresist, making holes in it, electrochemical deposition of metal islets into photoresist holes from electrolyte solution, and installation of prepared plate into growth furnace with further growing of silicon whiskers on it, at that cylindrical openings in photoresist are created with diameter of less than 250 nm by means of imprint-lithography, metal islets are deposited with thickness of less than 12.5 nm, after that photoresist is removed in 5% solution of hydrofluoric acid.

EFFECT: method makes it possible to considerably facilitate creation of nano-technological instruments on nano-crystals.

4 ex

 

The invention relates to the technology of semiconductor nanostructured materials, intended for the cultivation of regular systems of filamentous nanocrystals of silicon by the method of gas-chemical reactions in an open flow system.

Currently known way to create regularly-ordered systems of nanoscale whiskers (NC), uses the principle job of the same particle sizes of the metal of the activator. In [1] with a very small range of diameters in the process of pyrolysis of monosilane (SiH4+ 10%) have been grown silicon nonprobate using colloidal Au particles on the surface of the Si-SiO2. For this purpose, the substrate of SiO2besieged "nanoprobing" gold diameter 8,4±0,9 nm from a solution of colloidal gold. Then the substrate Si-SiO2with deposited gold particles were placed in a furnace. The lateral dimensions of the nanocrystals was: 6,4±1.2 nm; 12,3±2.5 nm; 20,0±2,3 nm and 31.1±2,7 nm. The disadvantage of this method [1] is a large variation in the diameters of the grown crystals (5÷30%) and the inability to provide the identity of the droplet sizes of colloidal gold.

The closest technical solution chosen as a prototype, is a method of growing regular NK silicon, as proposed in patent No. 2117081 [2]. The difference is in the way is that masking the surface of a silicon wafer by using photolithography with photoresist and the metal activator is applied by electrochemical deposition of islets of metal from the electrolyte solution. The disadvantage of this method is its unsuitability for generating regular systems of nanoscale NC with diameters less than 100 nm due to the physical limits applied by photolithographic methods, because you cannot apply the methods of photolithography in the photo resistor to form a cylindrical hole diameters substantially less than 250 nm. And the creation of holes in the photoresist with transverse dimensions much less than 250 nm is the main necessary condition for the formation of the same size of the nanoparticles of metal-activator Agrocomplex growth nano-whiskers.

The invention is directed to a controlled fabrication of periodic surface structures whiskers nanometer diameters.

This is achieved by the fact that before placing a silicon wafer in the growth furnace and the cultivation of her whiskers the surface of the silicon wafer photoresist mask, after which the photoresist using an imprint-lithography create cylindrical holes with a diameter of less than 250 nm, followed by deposition in these Islands of metal of a thickness of less than 12.5 is m from the electrolyte solution and removing the photoresist in a 5% solution of hydrofluoric acid.

The method of growing regular filiform nanocrystals of silicon having a diameter of less than 100 nm, as follows. On the surface of the monocrystalline silicon wafer by centrifuging put a layer of photoresist. Then, the photoresist using an imprint-lithography marked by engraving the hole (window) size. In the "window" electrochemically deposited metal impurities originating. Thus on the silicon wafer, which electrode is grown in columns (islets) of metal with a given ratio of height to diameter for the formation of each "window" only nanocable when soldering. Then the substrate is placed in a quartz reactor, purged with hydrogen, heated to a temperature of growth. Within a few minutes in hydrogen is fusing of the metal nanoparticles with the substrate. Then in the gas phase is fed feed material and the growing nanocrystals.

Application of the method, the imprint-lithography is determined by the fact that existing methods of photolithography does not allow element sizes less than 0.3 μm. The effectiveness of the imprint-lithography in our case is achieved by the fact that to create nanostructures, you need only one lithography process, which eliminates difficulties in reconciling dies for forming the various layers of structures, I have lausiaca main limitations in the use of the imprint-lithography method.

The diameter of the openings in the photoresist (250 nm or less) is determined by the ratio of the diameter of the holes of the metal melting-activator at the base of the filamentary crystal to the diameter of the crystal on the cylindrical section of monocrystalline silicon rod is 2.5. Thus, to obtain nanometer (100 nm or less) across the crystal, you must set 2.5 times greater base diameter NC.

The thickness of the electrolytic layer of sediment in the holes in the photoresist (12,5 nm or less) is determined by the fact that for the formation of a single drop of the solution-melt metal to silicon in the "window" you must ensure that the ratio of the thickness-diameter for islet metal 0,02-0,05 (depending on the type of metal).

Removal of residual photoresist in a weak aqueous solution of hydrofluoric acid after the electrochemical deposition of the metal due to the fact that HF simultaneously with the removal of the photoresist is etched layer of silicon dioxide and other impurities, the appearance of which the plate is possible on previous operations. Thus, together with the removal of the photoresist is cleaned silicon wafers from contamination.

Using the proposed method allows to significantly alleviate the problem of integral devices high density nanowires is (random access memory devices (computers), not preheat cathode emission devices, high density electron emission, the production of light-emitting devices, etc.

Examples of the method.

Example 1.

On a monocrystalline silicon wafer with a crystallographic orientation of {111} and diameters of 300 mm was applied sensitive to ultraviolet radiation photoresistive organic material, covering the surface of the crystal. Then, the photoresist using an imprint-lithography-known techniques of "printing" was formed system nanotori or "neocon". The diameter of each hole was 80 nm, and the distance between the centers of the holes 70 nm.

In a solution of phosphate electrolyte gilding open in "Windows" areas of a silicon wafer was deposited electrochemical layer of gold of a thickness of 3 nm. This plate served as a conductive cathode, the distribution potential of the entire area of the plate. Because the photoresist is dielectric, the electrolytic residue covers only the exposed areas. In order that the gold was not singled out for not obverse side of the wafer, it is covered with a dielectric protective varnish.

After deposition, the photoresist was removed in an aqueous 5% solution of hydrofluoric acid. On a silicon wafer formed regularly spaced Islands of metal-activator Odie is W hat size.

The prepared substrate was into fragments and placed in a growth furnace. Within 2-10 minutes at a temperature of 900-1100°was carried out With the alloying of gold with silicon and formed nanocable molten Au-Si. Then in the gas phase was filed silicon tetrachloride in a molar ratio of MSiCl4/MH2value =0.008 and grew filiform nanocrystals. The cultivation was (2-10 minutes depending on the desired height of the nanocrystals. The crystals had a diameter of 32±1 nm and a length of ˜200 nm.

Example 2.

The cultivation of filamentous nanocrystals was carried out analogously to example 1, but as a metal activator Agrocomplex-growth was used electrolytic Nickel. The thickness of the sediment layer was 5 nm. The metal deposition was carried out from a solution of Nickel chloride. Grown NC had a diameter of 30±1 nm and a length of ˜150 nm.

Example 3.

The implementation of the invention was carried out analogously to example 1, but the time of removal of the layer of photoresist in a 5% solution of hydrofluoric acid was increased in 5 times. The results obtained are consistent with the results of example 1.

Example 4.

The implementation of the invention was carried out analogously to example 1, but the thickness of the sediment layer was 10 nm, and the temperature of cultivation was 100 degrees below. The results obtained are consistent with the results of example 1, but the diameters of the nanocrystals part of the Yali 35± 1 nm.

List of used sources

1. Gudiksen, M.S., C.M. Lieber Diameter-selective synthesis of semiconductor nanowires // J. Am. Chem. Soc.; (Communication); 2000; 122(36); pp.8801-8802.

2. RF patent №2117081, IPC6SW 029/62, 025/02/ AA Schetinin, VA Nebolsin, A.I. Dunaev, E.E. Popova, PU Boldyrev.

The method of obtaining regular systems of nanoscale silicon whiskers, including the preparation of a silicon wafer by masking the surface of the photoresist, a hole, electrochemical deposition in the openings of the photoresist Islands of metal from the electrolyte solution, and placing the prepared plate in the growth furnace with subsequent cultivation on her whiskers, characterized in that the cylindrical openings in the photoresist to create a diameter of less than 250 nm imprint-lithography, the Islands of the precipitated metal thickness of less than 12.5 nm, and then remove the photoresist in a 5% solution of hydrofluoric acid.



 

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