RU2359356C1 - Method for creation of conducting nanowires on surface of semiconductor substrates - Google Patents

Abstract

FIELD: physics, semiconductors.

SUBSTANCE: invention is related to methods for creation of metal nanowires on surface of semiconductor substrates and may be used in creation of solid-state electronic instruments. Substance of invention: in method for creation of conducting nanowires on surface of semiconductor substrates, copper is deposited on surface of silicon Si(lll) with formation of buffer layer of copper silicide Cu₂Si at the temperature of 500°C under conditions of ultrahigh vacuum. Buffer layer of copper silicide is formed with monatomic thickness, afterwards at temperature of 20°C at least 10 layers of copper are deposited on atomic steps of buffer layer surface, which form nanowires of epitaxial copper that are oriented along atomic steps of substrate.

EFFECT: provides for creation of nanowires that possess high conductivity, with the possibility of these nanowires formation location control.

3 dwg

Description

The invention relates to methods for creating metal nanowires on the surface of semiconductor substrates and can be used to create solid-state electronic devices.

A known method of creating on the surface of silicon Si (100) nanowires based on rare-earth metal silicides (ScSi ₂ , ErSi ₂ , DySi ₂ , GdSi ₂ ), which consists in the deposition of films of rare-earth metals (Er, Gd, Sc, Dy) submonoatomic under ultrahigh vacuum thickness (less than 0.5 monoatomic layer) on a previously cleaned specified surface in the temperature range from room temperature to 620 ° C and subsequent annealing of the deposited film in the temperature range from 575 ° C to 800 ° C for 5 minutes to stimulate a chemical reaction between the deposited meth llom and the silicon substrate, resulting in anisotropy due to the silicide and the silicon substrate mismatch lattices (for ScSi _2, ErSi _2, DySi _2, GdSi ₂ mismatch is -4.6%, 6.3%, 7.6%, 8.9 %, respectively, in one of the main crystallographic directions Si <110> and 0.8%, -1.6%, -0.1%, 0.8%, respectively, in the direction perpendicular to it) to the anisotropic growth of islands of the silicide phase having the shape of nanowires having a width in the range of 3 to 11 nm, a height in the range of 0.2 to 3 nm, and a length in the range of 150 to 450 nm [Y. Chen et al., US Patent "Formation of nanoscale wires" No. 6,773,616 B1, Date of Patent: Aug. 10, 2004; Y. Chen, DAAOhiberg, RSWilliams, "Nanowires of four epitaxial hexagonal silicides grown on Si (100) ″ // Journal of Applied Physics 2002, v. 91, P. 3213-3218].

The disadvantage of this method is that the formation of nanowires occurs spontaneously in arbitrary places on the substrate, and their growth can occur equally in two perpendicular directions, and thus, this method does not provide the ability to control the location of the formation of nanowires on the surface of the substrate and the direction of their growth.

There is also a method of creating arrays of metal nanowires, which consists in the deposition of films of noble metals (Ag, Au), as well as lead (Pb), submonoatomic thickness on pre-cleaned vicinal Si (111) surfaces and high-index Si (557), under ultra-high vacuum conditions. characterized by a small width of atomic terraces (for example, 1.9 nm in the case of a Si surface (557)) and a high density of atomic steps (for example, 0.5 × 10 ⁹ m ^-1 in the case of a Si surface (557)), at a temperature in the range temperatures from 500 ° C to 700 ° C, as a result whose condensation of the deposited metal occurs at atomic steps with the formation of an array of nanowires of atomic thickness [I. Matsuda, M. Ueno, T. Hiraha, R. Hobara, H. Morikawa, C. Liu, S. Hasegawa, "Electrical resistance of a monoatomic step on crystalline surface "// Physical Review Letters, 2004, V. 93, P. 236801; H. Okino, R. Hobara, I. Matsuda, T. Kanagawa, S. Hasegawa, J. Okabayashi, S. Toyoda, M. Oshima, K. Ono, "Nonmetallic transport of a quasi-one-dimensional Si (557) -Au surface "// Physical Review In 2004, v. 70, p. 113,404; C. Tegenkamp, H. Pfnur, "Switching between one- and two-dimensional conductance: Coupled chains in the monolayer of Pb on Si (557)" // Surface Science 2007, v. 601, p. 2641].

The disadvantage of this method is that nanowires formed using this method have low conductivity due to the limited cross section of atomic thickness nanowires.

The problem to which the claimed method is directed to create conductive nanowires on the surface of semiconductor substrates is to develop the creation of nanowires with high conductivity, with the ability to control the location of the formation of these nanowires.

The problem is solved in that at the first stage of the creation of conducting nanowires, copper is deposited on the Si (111) silicon surface with the formation of a buffer layer of CuaSi copper silicide at a temperature of 500 ° C under ultrahigh vacuum, a buffer layer of copper silicide is formed of a monatomic thickness, and then at a temperature At least 10 copper layers are deposited at 20 ° C on the atomic steps of the surface of the buffer layer, which form epitaxial copper nanowires oriented along the atomic steps of the substrate.

Distinctive features of the claimed method for creating conductive nanowires on the surface of semiconductor substrates are:

- a buffer layer of copper silicide form a monoatomic thickness;

- at a temperature of 20 ° C, at least 10 layers of copper are deposited on the atomic steps of the surface of the buffer layer, which form epitaxial copper nanowires oriented along the atomic steps of the substrate.

A comparative analysis of the essential features of the claimed method with the essential features of analogues and prototype indicates its compliance with the criterion of "novelty." The claimed method has a technical level and may be suitable for use.

Moreover, the distinguishing features of the invention provide the possibility of controlled creation of nanowires with high conductivity on the surface of the semiconductor substrate.

Figure 1 presents a diagram of sequential operations in the inventive method of forming Cu nanowires on the surface of a silicon substrate Si (111). Figure 2 presents the image of the surface with an array of nanowires obtained in a scanning tunneling microscope. Figure 3 presents the measurement results.

The claimed method of creating conductive nanowires on the surface of semiconductor substrates is implemented as follows.

On the previously cleaned surface of silicon Si (111), a buffer layer is created, which is a silicide of Cu ₂ Si of monoatomic thickness, which has the property that Cu atoms deposited on the specified layer at room temperature do not enter into a chemical reaction with the silicon atoms of the substrate, and Migrating freely on the surface of atomic terraces, they condense on atomic steps, forming along them an epitaxial copper nanowire.

At the first stage (figa), by heating at a temperature of 1200 ° C for 20 s under ultrahigh vacuum <1 × 10 ^-7 Pa, an atomically clean Si (111) surface with a concentration of structural defects <3% is obtained.

At the second stage (figb), a copper film with a thickness of 2 monatomic layers (MS) is deposited on a cleaned surface without violating ultrahigh vacuum conditions. Copper is deposited from the effusion cell at a rate of 0.5 MS / min; the substrate temperature during deposition is 500 ° C. As a result of the reaction of deposited copper with silicon atoms, a continuous layer of copper silicide Cu ₂ Si of monoatomic thickness is formed on the surface of the substrate.

In the third stage (Fig. 1c), a copper film with a thickness in the range from 10 to 25 MS is deposited on the surface of the Cu ₂ Si buffer layer at room temperature, while the deposited copper condenses at the atomic steps to form epitaxial copper nanowires. The width of the nanowires is in the range from 20 to 40 nm, the height in the range from 1 to 2 nm. To characterize the conductivity of the formed array of nanowires using a probe head with four probes located at the vertices of the square with a side of 0.6 mm, we performed electrophysical measurements of the system conductivity as a function of the angle of rotation of the probe head. The circles show the data for the angular dependence of the conductivity of the sample before the growth of nanowires, i.e., a Si (111) substrate coated with a layer of silicide Cu ₂ Si of monoatomic thickness. The upward triangles represent the angular dependence of the conductivity of the sample with the formed array of nanowires during the deposition of 22 MS copper. The indicated dependence corresponds to the anisotropy of conductivity (the ratio of conductivity along and across the direction of nanowires), equal to 4.8. This value actually characterizes how many times the conductivity of nanowires is higher than the conductivity of the substrate. The triangles with the vertices downward represent the data on the angular dependence of the conductivity of the sample with a continuous copper film formed during the deposition of 28 Cu Cu. The conductivity of the film coincides with the conductivity of nanowires, but there is no anisotropy of conductivity in it. The table shows the value of the anisotropy of the conductivity of an array of nanowires obtained using the inventive method in comparison with those for arrays obtained using known methods. As can be seen, the anisotropy of conductivity in them, and, consequently, the conductivity of nanowires proper, is 1.8-3.0 times lower.

Comparison of anisotropy of electrical conductivity for various structures formed on the steps of the surface system anisotropy link Si (111) -Cu 4.8 Si (111) -Ag 1,6 [one] Si (557) -Au 2.7 [2] Si (557) -Pb 1,5 [3]

[1] I. Matsuda et al. Physical Review Letters 2004, v. 93, p. 236801.

[2] H. Okino et al. Physical Review In 2004, v. 70, p. 113404.

[3] C. Thegenkamp and H. Pfnur, Surface Science 2007, v. 601, p. 2641.

Thus, due to the use of a two-stage procedure of deposition of copper on the Si (111) silicon surface with the formation of a monoatomic thickness of a copper silicide Cu ₂ Si layer at a temperature of 500 ° С at the first stage and superposition of 10–20 monoatomic copper layers at the second stage at room temperature, it was possible to ensure the formation of epitaxial copper nanowires oriented along the atomic steps of the substrate and having a conductivity higher than that of known pototypes.

Claims (1)

The method of creating conductive nanowires on the surface of semiconductor substrates, which consists in the deposition of copper on the silicon surface Si (111) with the formation of a buffer layer of copper silicide Cu ₂ Si at a temperature of 500 ° C under ultra-high vacuum, characterized in that the buffer layer of copper silicide form a monoatomic thickness then, at a temperature of 20 ° С, at least 10 copper layers are deposited on the atomic steps of the surface of the buffer layer, which form epitaxial copper nanowires oriented along the atomic steps of the substrate .

Images