RU2453874C1 - Method of forming flat smooth surface of solid material - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to micro- and optoelectronic engineering. In the method of forming a flat smooth surface of a solid material, a hole is formed on the substrate of the solid material with parts of the surface deviating in diametrically opposite directions, which ensure opposite direction of fronts of atomic stages. Thermoelectric annealing is carried out by passing electric current whose value causes resistive heating of the substrate material to temperature of activated sublimation of atoms of the top atomic layer with movement on the surface of monoatomic stages. During annealing, the working surface is cleaned from natural oxide and contaminants. The main step or main and additional steps of thermoelectric annealing are then carried out in a vacuum of 10^-8 Pa. Current is passed in parallel to the working surface of the substrate during a period of time and under temperature conditions which form, on the periphery of the inner part of the hole, accumulation of monoatomic stages with high density, with the emergence of single concentric monoatomic stages uniformly distributed on the periphery of the inner part of the hole and separated by a singular terrace. Supply of electric current is cut off and temperature of the substrate is lowered.

EFFECT: obtaining atomically smooth surfaces, reducing roughness to 0,4 Å, controlling the size of the flat smooth surface and increase thereof across by 100-300 mcm.

9 cl, 3 dwg

Description

The invention relates to the technology of micro- and optoelectronics, to microstructural technology, to nanotechnology, to optical instrumentation, to fields of technology, in particular, with high demands on the smoothness of surface treatment of materials such as semiconductors, metals, dielectrics, including both substrates and thin films, and can be used to create micro- and nanodevices requiring atomically smooth surfaces, as well as for the manufacture of dielectric and metal-dielectric mirrors, for example, based on ve silicon, including interference microscope and laser processing systems based on gas, semiconductor, solid-state lasers and other light sources.

A known method of forming a flat smooth surface of a solid-state material (US patent No. 6805807, IPC: 7 H01L 21/302), which consists in the fact that the substrate of the solid-state material is exposed to adaptive beams of ion clusters, reducing surface roughness, thereby forming a smooth surface using a sequential etching the surface of the substrate with high and low energy argon ions, wherein the substrate is first treated with a beam of high energy argon ion clusters to remove large irregularities, with a high etching rate, over a period of time ensuring the achievement of the residual roughness limit determined by the beam energy, after which the beam parameters are tuned to reduce the etching rate and proceed to etching the substrate material with lower ion energy values until the next limit of the residual surface roughness is reached. A silicon wafer with a copper film deposited on its surface is used as a substrate.

Using the above method, relatively smooth surfaces are formed, reducing the roughness from Ra = 100 Å to Ra = 11 Å.

The disadvantages of this known technical solution are the fundamental impossibility of obtaining atomically smooth surfaces, the fundamental presence of high roughness of the resulting flat smooth surface, significantly exceeding 0.4 Å.

A known method of forming a flat smooth surface of a solid-state material (US patent No. 6806199, IPC: 7 H01L 21/302), which consists in the fact that the substrate of the solid-state material is subjected to thermal annealing in an argon atmosphere. A silicon wafer is used as the substrate. During annealing, the concentration of silicon crystal growth defects decreases, due to which the surface of the substrate acquires relative smoothness.

The surface roughness was measured by atomic force microscopy; the roughness was about 0.11 nm over an area of 2 μm × 2 μm (Rms).

The disadvantages of this known technical solution, as well as the first of the above analogues, are the fundamental impossibility of obtaining atomically smooth surfaces, the high roughness of the resulting flat smooth surface, significantly exceeding 0.4 Å. When the method is implemented, the surface of the substrate is contaminated by thermal annealing in an argon atmosphere containing impurities. Also, in the process of annealing, a developed relief is formed on the surface with a characteristic size Rmax = 1.5 nm.

A known method of forming a flat smooth surface of a solid-state material (Appl. Phys. B. (2008) 93: 55-57), which consists in the fact that the substrate of a solid-state material is placed in a near-field optical microscope in a chlorine-containing atmosphere, which is exposed by a gas laser in the mode continuous radiation with a wavelength of 532 nm, exciting a photochemical reaction leading to the dissociation of chlorine molecules, and generating an optical near field on the surface of the substrate, initiating non-adiabatic reactions with Cl ₂ molecules and leading to selective etching of surface irregularities with the formation of a flat smooth surface, characterized by a minimum average roughness Ra = 1.17 Å. The substrate used is a quartz substrate obtained by gas-phase deposition, after having subjected the substrate to chemical-mechanical polishing. The diameter of the substrate is 30 mm. When initiating non-adiabatic reactions with Cl ₂ molecules and selective etching of the surface irregularities of the substrate, the pressure of the chlorine-containing atmosphere is maintained at 100 Pa; the temperature is set at room temperature. The etching time is chosen up to 120 minutes or more. Etching is carried out in scanning mode on the surface of the substrate.

Assessment of surface roughness before and after the formation of flat smooth surfaces was evaluated using an atomic force microscope. The roughness of the substrates before etching was 2.36 ± 0.02 Å. After etching the substrates for 120 minutes, the roughness decreased to a minimum value of 1.37 Å.

The disadvantages of this well-known technical solution are the impossibility of obtaining atomically smooth surfaces, not to mention the possibility of controlling their size, the high roughness of the resulting flat smooth surface, significantly exceeding 0.4 Å. The reasons for the shortcomings are fundamental. The formation of a smooth surface is based on the chemical interaction of the substrate material with the process medium, which prevents the achievement of the following technical result.

For the closest technical solution to the claimed method of forming a flat smooth surface of a solid-state material (Y. Homma et. Al., Phys. Rev. B, 55, 16, 1997), which consists in the fact that on the working surface of the substrate of the solid-state material craters are formed with vertical walls, after which conduct thermoelectric annealing of the substrate. The substrate of solid state material is subjected to ion beam treatment with oxygen ions with an energy of 10.5 keV, leading to etching of the substrate material and forming craters with a flat bottom of 150 μm × 150 μm in size and vertical walls, after which the substrate is sequentially treated in H ₂ SO ₄ solutions: H ₂ O (4: 1) and HF several times until the particles of contamination are removed from the surface, completing the oxidation treatment in the indicated aqueous solution of sulfuric acid, then the substrate is placed in an ultrahigh-vacuum scanning electron microscope, in which By transmitting direct electric current, they conduct their thermoelectric annealing, which leads at elevated temperatures to the formation of flat smooth surfaces at the bottom of craters - terraces with a diameter of up to 70 microns in diameter. As the substrate, a silicon substrate of orientation (111) is used.

The disadvantages of the closest technical solutions include: the inability to obtain atomically smooth surfaces of a large area, the inability to control their size; limiting the area of the resulting smooth surface to a maximum value of 70 microns in diameter; the roughness of the formed flat surface, significantly exceeding 0.4 angstroms. The reasons for these shortcomings are as follows.

The limitation in the maximum size of the obtained flat smooth surfaces is due to the finite size of the craters formed during ion beam etching by oxygen ions and the limited length of the migration of adatoms on the crystal surface (silicon substrate) during thermoelectric annealing.

The presence of vertical walls of the craters is a significant factor in limiting the size of the resulting flat surfaces. Vertical walls rigidly determine the location of incorporation of monatomic steps during thermoelectric annealing, causing sublimation of atoms of the upper atomic layer and the movement of monatomic steps on the surface, which results in the formation of flat surfaces. They set the boundaries within which the movement and integration of monoatomic steps is possible. Thus, the area bounded by the vertical walls of the craters - the bottom area cannot be increased. The maximum size of flat smooth surfaces is limited by the finite size of the craters.

On the other hand, although the technical solution under consideration uses the self-organization of monatomic steps on the surface of the substrate during the annealing process, this use is made in an uncontrolled manner, without the ability to control the length of migration of adatoms on the surface of the substrate. The absence of control over the length of the migration of adatoms (the length of diffusion over the surface of the terrace) makes it impossible to control the size of the formed atomically smooth surface.

In addition, the use of chemical etching when cleaning the surface of the substrate before placing it in ultrahigh vacuum to conduct thermoelectric annealing in order to form atomically smooth surfaces causes the appearance of uncontrolled micro roughnesses over a large area and the inability to obtain atomically smooth surfaces with a large area.

The technical result of the invention is:

- obtaining atomically smooth surfaces;

- reduction of the roughness of the formed flat surface to 0.4 angstroms;

- achieving the ability to control the size of the formed flat smooth surface, including its increase to a value exceeding 100 microns in diameter.

The technical result is achieved in a method for forming a flat smooth surface of a solid-state material, which consists in conducting thermoelectric annealing of the substrate, before conducting thermoelectric annealing on the working surface of the substrate of the solid-state material, a hole is formed consisting of portions of the surface of the substrate deflected in diametrically opposite directions from the working surface of the substrate providing the opposite direction of the fronts of atomic steps, when thermoelectric During annealing, a constant or alternating electric current is passed, which causes the resistive heating of the substrate material to the temperature of activated sublimation of the atoms of the upper atomic layer with the movement of monoatom steps along the surface, and first, preliminary, cleaning the working surface of the natural oxide of the substrate material and / or contaminants, annealing, which is the initial stage of thermoelectric annealing, then carry out the main stage of thermoelectric annealing or conduct the main n thermoelectric annealing and an additional step of thermoelectric annealing, all thermoelectric annealing is carried out in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material into vacuum, an electric current is passed parallel to the working surface of the substrate, for a period of time and under the temperature regime forming along the periphery of the inner part of the well, formed by sections of the surface of the substrate deflected in diametrically opposite directions relative to its size side surface, the accumulation of monoatom steps with a high density, with the characteristic appearance of single concentric monoatom steps evenly distributed along the periphery of the inner part of the well, separated by a singular terrace, with a controlled width located in the central part of the well, after the main stage of thermoelectric annealing, the temperature regime with respect to the substrate they change, the supply of electric current is stopped and the substrate temperature is reduced to room temperature at a speed that preserves the distribution of monatomic steps resulting from the main stage of thermoelectric annealing, with the absence of generation of new atomic steps, ultimately preserving the size of the singular terrace in the central part of the hole, or after the main stage of thermoelectric annealing, the supply of electric current is limited and the substrate temperature is reduced at a speed preserving the distribution of monatomic steps obtained as a result of the main stage of thermoelectric annealing, with no gene radiations of new atomic steps, to a temperature which is characterized by the absence of generation of new atomic steps, but with respect to which the electromigration of atoms has not stopped, and through an additional step of thermoelectric annealing at the indicated temperature, with the flow of atoms of the substrate material onto the substrate, increasing the length of atomic electromigration, additionally increase the size of the singular terrace obtained in the main part of the electrothermal annealing in the central part of the hole, annealing for a period of time sufficient to obtain the required size, and then cooled to room temperature at a rate that preserves the distribution of monatomic steps obtained as a result of an additional step of thermoelectric annealing, without the generation of new atomic steps, and ultimately preserves the size of the additionally enlarged singular terrace in the central part of the hole.

In the method, a silicon substrate with a working surface orientation (111) or a silicon substrate with a vicinal working surface (111) with a misorientation angle of 0 ° 0'20 "to 5 ° is used as a solid state material substrate.

In the method, a hole is formed consisting of portions of the substrate surface deflected relative to the working surface of the substrate in diametrically opposite directions, providing opposite directions of the fronts of the atomic steps, in that the substrate is subjected to ion beam treatment with Ar ions with energies from 1 to 7 keV for a period of time from 1 to 360 minutes in a vacuum at a level sufficient to inhibit the effect of residual gas during the ion-beam treatment, namely, not more than 10 ^-3 Pa, the processing substrate rot yields relative to an axis directed perpendicular to the working surface of the substrate, with a frequency of from 0.1 to 100 Hz, the ion beam is directed at an angle to the working surface of the substrate, providing the dimensions of the hole necessary to obtain the required area of a flat atomically smooth surface, namely, providing surface sections deviated in diametrically opposite directions with a deviation angle from 0 ° 0'10 ”to 15 °.

In the method, thermoelectric annealing is carried out in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material into the vacuum, namely, characterized by a residual pressure of not more than 10 ^-8 Pa.

In the method, preliminary annealing is performed, which cleans the working surface of natural oxide of the substrate material and / or contaminants, which is the initial stage of thermoelectric annealing, passing an electric current of a value corresponding to heating to a temperature from 1250 ° C to 1410 ° C for a minute or more.

In the method, the main stage of thermoelectric annealing is carried out, in which direct or alternating electric current is passed by a value causing resistive heating of the substrate material to the temperature of activated sublimation of the atoms of the upper atomic layer with movement along the surface of monatomic steps, the electric current is passed parallel to the working surface of the substrate for a period of time and at temperature conditions, forming along the periphery of the inner part of the hole formed by deflected diametrically and in opposite directions by the surface areas of the substrate relative to its working surface, the accumulation of monoatomic steps with high density, with the characteristic appearance of single concentric monoatomic steps evenly distributed along the periphery of the inner part of the well, separated by a singular terrace, with a controlled width located in the central part of the well, namely, up to temperature conditions from 832 ° C to 1410 ° C and a period of time from 8 to 14000000 seconds, with the corresponding lower heating temperature under ozhki greater the annealing time, with decreasing values at intermediate temperature range of said annealing time proportional to the increase in temperature.

In the method, after the main stage of thermoelectric annealing, the temperature regime in relation to the substrate is changed, the supply of electric current is stopped and the temperature of the substrate is reduced to room temperature at a rate that preserves the distribution of monatomic steps obtained as a result of thermoelectric annealing, with the absence of generation of new atomic steps, ultimately, which preserves the size of the singular terrace in the central part of the hole, namely, at a speed of 0.1 to 400 ° C / s.

In the method, after the main stage of thermoelectric annealing, the temperature regime with respect to the substrate is changed, the supply of electric current is limited and the temperature of the substrate is reduced at a rate that preserves the distribution of monatomic steps obtained as a result of thermoelectric annealing, with no generation of new atomic steps, namely, from 0.1 to 10 ° C / s, to a temperature which is characterized by the absence of generation of new atomic steps, but with respect to which the electromigration of atoms has not stopped, namely, to a temperature equal to d from 832 ° С to 1100 ° С, and an additional thermoelectric annealing step is carried out, in which direct or alternating electric current is passed by a value causing resistive heating of the substrate material to the temperature of activated sublimation of the atoms of the upper atomic layer with movement along the surface of the monatomic steps, electric current is passed parallel to the working surface of the substrate, over a period of time and under temperature conditions, forming along the periphery of the inner part of the hole, formed deflected in opposite directions of the surface of the substrate relative to its working surface, the accumulation of monatomic steps with a high density, with the characteristic appearance of uniform concentric monoatomic steps evenly distributed around the periphery of the well, separated by a singular terrace, with a controlled width located in the central part of the well, through an additional step thermoelectric annealing at the specified temperature, with the flow of atoms of the substrate material n a substrate that increases the length of atomic electromigration, namely, a stream that ensures the deposition rate of atoms on the substrate surface from 0.01 to 0.02 monolayers / s, further increase the size of the resulting singular terrace in the central part of the well, annealing for a period of time sufficient to obtain the required size, namely, for a period of time equal to from 1 minute to 10 hours, with the correspondence of a larger time to a lower temperature of additional thermoelectric annealing, and then cooled to room temperature temperatures at a rate that preserves the distribution of monatomic steps obtained as a result of additional thermoelectric annealing, with the absence of generation of new atomic steps, and ultimately preserves the size of the additionally enlarged singular terrace in the central part of the well, namely, at a speed of 10 to 400 ° C /from.

In the method, lowering the temperature of the substrate or lowering the temperature of the substrate and carrying out an additional step of thermoelectric annealing with a further decrease in the temperature of the substrate to room temperature is carried out in vacuum with a level sufficient to suppress the effect of residual gases and the release of atoms of the substrate material into vacuum, namely, characterized by a residual pressure of not more than 10 ^-8 Pa.

The invention is illustrated by the following description and the accompanying figures.

Figure 1 schematically shows the sequence of the main stages of the formation of a flat smooth surface of a solid-state material: a) the initial stage; b) the stage of formation on the working surface of the substrate of a region containing surface areas deviated from the original working surface of the substrate with a given crystal orientation in diametrically opposite directions at the same angle, or wells by ion beam etching by a beam of low-energy argon ions directed at an angle to the working surface of the substrate, placed in the holder, providing rotation of the substrate relative to the axis perpendicular to the working surface of the substrate; c) the stage of cleaning the working surface of the substrate from natural oxide and contaminants by heating it to 1300 ° C by passing a constant or alternating electric current parallel to the working surface of the substrate, characterized by the movement of steps on the surface of the substrate in the direction from the lower terrace, the least remote from the non-working surface of the substrate, to the highest terrace, farthest from the non-working surface of the substrate, due to the sublimation of atoms; d) the stage of formation of a singular atomically smooth portion on the working surface of the substrate with a size of about 100 μm in diameter during thermal annealing, for example, at a temperature of 900 to 1350 ° C, by passing an electric current parallel to the working surface of the substrate for a period of at least 60 seconds ; where 1 is the substrate, 2 is the layer of natural oxide, 3 is the holder, 4 is the ion source, 5 is the vacuum chamber, 6 are surface sections deviated in diametrically opposite directions, 7 are the holders providing electrical contact, 8 is the power source, 9 is monatomic steps, 10 - lower terrace.

Figure 2 schematically shows the redistribution of monatomic steps (0.314 nm high) on portions of the surface of the substrate deflected in diametrically opposite directions relative to the working surface of the substrate while transmitting electric current, which leads to resistive heating of the substrate: a) image of the initial distribution of monatomic steps that limit terraces orientation (111), on the working surface of the substrate after cleaning by high-temperature annealing while passing an electric current with upper monoatoms and steps (height of 0.314 nm) bordering the terraces width 0.3 ± 0.2 mm, and a central, lower, least remote from the broken surface of the substrate, terrace widths d _1; b) - d) - the dynamics of the process of increasing the lower terrace, the least distant from the non-working surface of the substrate; where 9 are monatomic steps, 10 is the lower terrace, 11 is a cluster of closely spaced monatomic steps separated by narrow terraces.

Figure 3 presents: a) an image of the working surface of a silicon (111) substrate with an atomically smooth surface, obtained using optical microscopy, in which the accumulation of closely spaced monatomic steps limits the area with an atomically smooth surface; b) a topographic image of a portion of an atomically smooth surface obtained by atomic force microscopy, in which the lower terrace, the most distant from the working surface of the substrate, representing the formed atomically smooth surface, is limited to atomic steps; where 10 is the lower terrace, 11 is a cluster of closely spaced monatomic steps separated by narrow terraces.

The method provides the formation of a flat atomically smooth surface with controlled roughness and lateral size as a result of the organization on the stepped surface of the substrate of a solid material, for example, silicon with a crystalline orientation (111), of morphological features in the form of concentric monatomic steps with a controlled density per unit area, limiting a wide (more than 100 microns in diameter) a terrace with a roughness of not more than 0.4 angstroms (Ra).

The implementation of the method and the achievement of the indicated technical result are based on the rejection of the traditional approach to obtaining a smooth surface by chemically affecting the substrate material of the technological environment, the transition to the use of self-organization of monatomic steps on the surface of the substrate during thermal annealing of the substrate by passing electric current through the substrate, and the use of the self-organization process is carried out in a controlled manner, which ensures receipt on the working surface solid-state substrate the required features of the relief. The possibility of control with respect to obtaining the required relief features - wide terraces (about 100 μm in diameter or more), characterized by a roughness of not more than 0.4 Å, limited by concentric monoatom steps, is achieved by controlling the temperature regime of the substrate during thermoelectric annealing due to a controlled change in the transmitted through an electric current substrate. In particular, when the required width of the singular terrace appears - a formed flat atomically smooth surface as a result of resistive heating of the substrate material to the temperature of activated sublimation of the atoms of the upper atomic layer and movement along the surface of the monatomic steps, the substrate temperature is reduced to room temperature by a controlled decrease in the transmitted electric current corresponding to condition for maintaining the required distribution of atomic steps on the substrate and, as a consequence, maintaining the a preformed atomically smooth surface of the required area. The achievement of this roughness, not more than 0.4 Å, is provided by a preliminary short-term thermoelectric annealing, carried out before the main thermoelectric annealing, forming an atomically smooth surface. Preliminary annealing is carried out to clean the surface of natural oxide and contaminants, ensuring the presence of roughness to one degree or another.

The possibility of the aforementioned controlled self-organization of monatomic steps, which determines the required distribution of atomic steps on the substrate and obtain atomically smooth surfaces of the required area, is provided by controlling the diffusion length of the substrate adatoms by means of the temperature of the substrate or by combining the temperature of the substrate and supplying an additional stream of atoms of the substrate material to the latter. The physics of the process on the example of a silicon substrate with the orientation of the working surface (111), in particular, a substrate with a vicinal surface (111) with a misorientation angle of less than 1 °, is as follows.

A substrate (1) that has undergone standard chemical treatment that removes contamination particles (washing in distilled water, isopropyl alcohol and petroleum ether) and subjected to ion-beam exposure in a vacuum chamber (5) to form a well containing sections of the substrate surface deflected relative to the working surface substrates in diametrically opposite directions (see Fig. 1a) and b)) to ensure the opposite direction of the fronts of atomic steps, under ultrahigh vacuum vacuum chamber (5) (see Fig. 1 c) and d)) are subjected to thermoelectric annealing, including preliminary annealing and main annealing (see Fig. 1c) and d)), and also, if necessary, combined with the flow of atoms of the substrate material to its surface and additional annealing by passing through the substrate (1) electric current. The latter causes resistive heating of the substrate material (1) to the temperature of activated sublimation of the atoms of the upper atomic layer and the movement on the surface of monatomic steps. The temperature of the substrate (1) is controlled by the magnitude of the transmitted current, which is calibrated using a thermocouple at low temperatures (less than 800 ° C) and using an optical pyrometer at high temperatures (more than 800 ° C). The criteria for the purity of the substrate surface are the presence of a reversible superstructural transition (7 × 7) - (1 × 1) at a temperature of 830 ° C, the absence of centers of inhibition of steps during step motion during sublimation, and the absence of additional reflections in the diffraction pattern.

The working surface of the silicon substrate with the (111) orientation, purified from foreign impurities and oxide, is a system of periodically arranged monatomic steps with a height of 0.314 nm. By a monoatomic step is meant a continuous line delimiting two half-planes, with a height difference of one interplanar distance. If an electric current is passed through a silicon substrate with such a surface to a value sufficient to resistively heat it to a temperature of about 1000 ° C, the sublimation of atoms of the upper atomic layer (adatoms) activated in this case causes the movement of monatomic steps on the surface.

The sublimation process is divided into several stages: initially, the atom is localized in the kink of the step, then it breaks out of the kink, diffuses along the edge of the step, breaks away from the step and becomes an adatom. The adatom diffuses on the terrace during the lifetime τ _s , after which it sublimates. The equation describing the surface diffusion of adatoms along the terrace has the form:

,

,

where ρ (r, t) is the density of adatoms;

1 / τ _s - coefficient characterizing the probability of the process of atom detachment from the terrace during evaporation;

D _s - diffusion coefficient of adatoms on the terrace surface.

In equation (1), the effect of clustering of adatoms is not taken into account, since the union of two or more adatoms on the surface during sublimation is an unlikely process.

The process of sublimation in the conditions of exchange of adatoms between a step and terraces is accompanied by the movement of steps in the direction of overlying terraces. The shift of parallel steps equally spaced from each other by a distance equal to the width of the terraces corresponds to the removal of one monolayer of atoms from the surface of the crystal.

If the distance between the steps is greater than the diffusion length of the adatom (d> λ _s ), then the velocity of the atomic step υ is described by the expression:

,

,

where W is the activation energy of the sublimation process;

P is the vapor pressure in the gas phase;

P ₀ - equilibrium vapor pressure in the gas phase;

k is the Boltzmann constant;

T is the temperature;

λ _s is the diffusion length of the adatom;

ν is the characteristic frequency of the thermal vibrations of the lattice.

For d <λ _s , when the size of the terraces is small compared with the diffusion length of the adatom, the speed of the steps is proportional to the distance between the steps:

,

,

where W is the activation energy of the sublimation process;

P is the vapor pressure in the gas phase;

P ₀ - equilibrium vapor pressure in the gas phase;

k is the Boltzmann constant;

T is the temperature;

d is the distance between the steps;

ν is the characteristic frequency of the thermal vibrations of the lattice.

In this case, the value of the underlying terrace adjacent to it is of decisive importance for the speed of movement of a particular step. The formation on the surface of the region where the steps approaching form a site with a high density of their location due to the fact that some of them move faster than others towards the upper terraces, based on the proportionality of the speed of the steps from the width of the underlying adjacent terraces. The smaller the size of the underlying adjacent terrace to a particular step, the lower the speed of movement of the last

The last expression allows us to determine the activation energy of the sublimation process W = 4.2 ± 0.2 eV. The obtained value is close to the enthalpy of sublimation of silicon.

As a result of thermoelectric annealing in the inner part of the well, formed by portions of the substrate surface deflected relative to the working surface of the substrate in diametrically opposite directions, obtained after ion-beam irradiation, a system of concentric two-dimensional negative islands is formed, which are etching pits with a depth of one interplanar distance (see Fig.1d), Fig.2, a schematic representation of the surface topography - Figa)). In the central part of the hole (see Fig. 2a), the embryo of a two-dimensional negative island is localized, which appeared when the lower terrace (10) reached a critical size. A theoretical analysis of the nucleation of negative two-dimensional islands during the sublimation of crystal atoms shows that the nucleation of macrovacancy on the surface occurs under the condition:

,

,

where l is the distance between the steps;

γ is the linear tension coefficient;

λ _S is the diffusion length of the adatom,

k _B is the Boltzmann constant;

T is the temperature.

We estimate the right-hand side of the inequality described by expression (4). At a substrate temperature of about 1100 ° С on the silicon (111) surface, the linear tension coefficient of the step is γ≈0.39 eV / atom, and therefore, the ratio γ / k _B T≈3. Thus, the diffusion length of the adatom λ _S under these conditions is approximately three times less than the critical size of the terrace at which the nucleation of a two-dimensional island occurs. Further, using this ratio, we can estimate the length of migration of the adatom over the silicon (111) surface depending on the temperature: λ _S ≈ (2/3) Т. The higher the temperature of the substrate (1), the greater the diffusion length of the adatom and the greater the speed of the steps (see expression (2)), while the width of the underlying terraces is greater than the diffusion length of the adatom.

On the other hand, an increase in the diffusion length of an adatom with increasing substrate temperature by increasing the transmitted electric current competes with an increase in the sublimation of adatoms at the temperature increase, as a result of competition, the distance the adatom migrates with increasing temperature decreases. Due to sublimation, the adatom does not have time to migrate over a large distance on the terrace, although its diffusion length is potentially significant. The average displacement of the adatom λ _s along the surface of the crystal is described by the Einstein relation:

,

,

where D _S is the coefficient of surface diffusion of the adatom,

τ _S is the average lifetime of an atom in an adsorbed state.

A decrease in the diffusion length with increasing temperature is usually associated with a decrease in the lifetime of the adatom due to a more intense sublimation outflow of atoms from the surface of the crystal. We find that both varying the length of the diffusion of the adatom and intensifying the sublimation outflow of adatoms from the terrace accelerate the movement of monatomic steps on the surface, providing a more dense arrangement of the steps with the narrowness of their terraces. Thus, the density of the steps in the inner part of the hole (see Figure 2) is determined by the temperature of the substrate.

Upon reaching the required size of the formed atomically smooth surface in the central part of the well, bordered by monatomic steps located with one or another density on the periphery of the well, in order to avoid nucleation of new monatomic steps, the temperature of the substrate is reduced, reaching a mode at which the diffusion length of the adatom decreases.

The formation of the substrate region with the required density of monatomic steps along the periphery of the inner part of the well, as shown by the above reasoning, is based on the use of a controlled change in the diffusion length of the adatom from temperature during thermoelectric annealing and nothing more. In the proposed method, it is possible to control the distribution of monoatom steps of the pores of the periphery in the inner part of the well so that terraces with sizes from 0.1 to 300 microns are formed on the surface of the substrate.

In addition to the ability to control the diffusion length of the adatom due to the temperature of the substrate, which leads to an increase in the maximum size of a planar atomically smooth surface to 100 μm, it is possible to control the diffusion length of adatoms by connecting the flow of atoms of the substrate material, in particular, silicon, to the temperature factor, which additionally increases the diffusion length of adatoms. The indicated increase in the diffusion length occurs as a result of an increase in the lifetime of adatoms during the deposition of silicon. The lifetime of an adatom increases because the probability of annihilation of an adatom with surface vacancies decreases and a quasi-equilibrium surface concentration of adatoms is established.

Due to the fact that the proposed technical solution is physically based on the temperature dependence of the diffusion length of the adatom, the possibility of varying the latter by using one or another temperature regime during thermoelectric annealing of the substrate or by combining the temperature regime with the flow of silicon atoms to the substrate surface, for example, to obtain the desired the size of the atomically smooth surface, the restriction inherent in the prototype is removed in the maximum size of the obtained flat smooth x surfaces, due to the finite size of the craters formed by ion beam etching by oxygen ions.

In addition, with the same initial dimensions of the bottom of the craters and holes that form the ion-beam etching of the substrate material, the method shown as a prototype provides significantly smaller dimensions of the formed atomically smooth surfaces compared to the proposed method. In the proposed technical solution, the size of the source wells does not affect the final result. With the same initial bottom size or hole size, choosing the appropriate temperature regime for thermoelectric annealing of the substrate, as well as combining the selection of the temperature regime of annealing with the flow of atoms of the substrate material onto the substrate surface, it is possible to obtain different areas of atomically smooth surfaces.

So, the method of forming a flat atomically smooth surface of a solid-state material includes the following (see Figure 1).

Firstly, obtaining the initial hole, consisting of sections of the surface of the substrate, deflected relative to the working surface of the substrate in diametrically opposite directions, providing the presence of oppositely directed fronts of the steps (see Fig.1b).

The substrate (1), which underwent the initial standard chemical treatment, from which contaminants were removed, but a layer of natural oxide is present (2), is installed in the holder (3) (see Fig. 1a)) for ion-beam treatment from an ion source ( four). The ion source (4) and the substrate (1), mounted on the holder (3), are placed in a vacuum chamber (5). The vacuum level in the vacuum chamber (5) is set sufficient to suppress the influence of residual gases during ion-beam treatment, namely, not more than 10 ^-3 Pa.

The initial well is made, which consists of sections of the surface of the substrate deflected relative to the working surface of the substrate in diametrically opposite directions, ensuring the presence of oppositely directed fronts of the steps (see Fig. 1b). The substrate (1) is subjected to ion radiation, causing etching of the substrate material (1), while the holder (3) provides rotation of the substrate (1) relative to the axis directed perpendicular to the working surface of the substrate, with a frequency of from 0.1 to 100 Hz. The ion beam is directed at an angle to the working surface of the substrate (1) to provide the dimensions of the hole necessary to obtain the required area of a flat atomically smooth surface. In particular, to ensure the presence of surface sections (6) deviated in diametrically opposite directions (see Fig. 1c)), with an angle of deviation from 0 ° 0'10 ”to 15 °. The etching of the substrate material (1) is carried out, in particular, by a low-energy beam of argon ions with an energy of 1 to 7 keV for 1 ÷ 360 minutes. You can use other ion beams, for example, oxygen, as in the prototype.

Further, to conduct thermoelectric annealing, the substrate (1) with natural oxide present on its working surface and a well made, characterized by the presence of surface sections (6) deviated in diametrically opposite directions, is mounted, clamping it for reliable electrical contact, in conductive (metal) holders providing electrical contact (7), which are connected to a power source (8) (see Fig.1B)).

Thermoelectric annealing is carried out, including preliminary annealing, main annealing (see Fig. 1c) and d)), as well as additional annealing, by passing an electric current through the substrate (1). The substrate (1) with natural oxide present on its working surface and a well made, characterized by the presence of surface sections deviated in diametrically opposite directions (6), together with the holders providing electrical contact (7), are placed in a vacuum in a vacuum chamber (5) with a level sufficient to suppress the effect of residual gases and the release of atoms of the substrate material into the vacuum during thermoelectric annealing. The indicated vacuum level, in particular, is characterized by a residual pressure of not more than 10 ^-8 Pa.

Thermoelectric annealing is carried out, in which constant or alternating electric current is passed through the substrate (1), causing the resistive heating of the substrate material to the temperature of activated sublimation of the atoms of the upper atomic layer with the movement of monatomic steps on the surface. First, preliminary annealing is carried out in order to clean the substrate (1) from surface natural oxide and contaminants (see FIG. The temperature is controlled by the magnitude of the transmitted current from the power source (8). The values of the transmitted current are calibrated in the range of low, up to 800 ° C, temperatures using a thermocouple, in the range of high, more than 800 ° C, temperatures - using an optical pyrometer. The criterion for surface cleanliness is the presence of a reversible superstructural transition (7 × 7) - (1 × 1) at a temperature of 832 ° C, the absence of centers of inhibition of steps during their movement during sublimation, and the absence of additional reflections in the diffraction pattern.

When cleaning, it is important to have a sublimation process during thermoelectric heating of the substrate (1), due to which the removal of natural oxide and contaminants is carried out. Steps on the surface of a silicon substrate (substrate (1)), for example, with a (111) orientation, move along the surface towards overlying terraces due to the sublimation process of separating atoms of the substrate material (1) from the step, migrating them to the terrace, and separating them from the terrace and their exit from the surface into the surrounding substrate (1) the space of the vacuum chamber (5).

After cleaning, proceed to the main annealing. During basic thermoelectric annealing, direct or alternating electric current is passed through the substrate (1) from the power source (8), causing the resistive heating of the substrate material (1) to the temperature of the activated sublimation of the atoms of the upper atomic layer moving along the surface of the steps, the current is passed until the required relief features. Electric current is passed parallel to the working surface of the substrate (1). The transmission of electric current, accompanied by heating of the substrate (1), is carried out over a period of time, forming on the periphery of the inner part of the hole formed by surface sections (6) of the substrate (1) deviated in diametrically opposite directions relative to its working surface, an accumulation of monoatom steps with a high density , with the characteristic appearance of single concentric monoatomic steps evenly distributed over the periphery of the inner part of the well (9), separated by a singular terrace , Controlled widths (lower terrace (10) (see. 1D) and 2)) located in the central part of the hole. The operating temperature range provided by the resistive heating of the substrate material, causing activated sublimation of the atoms of the upper atomic layer with movement along the surface of the steps while passing an electric current, is from 832 ° C to 1410 ° C. The amount of time required for the formation on the periphery of the inner part of the hole, formed by sections of the surface (6) of the substrate (1) deflected in diametrically opposite directions relative to its working surface, accumulations of monatomic steps with a high density, with the characteristic appearance of uniformly distributed along the periphery of the inner part of the hole single concentric monoatomic steps (9) separated by a singular terrace, with a controlled width located in the central part of the hole, ulation from 8 to 14,000,000 seconds. Moreover, a lower heating temperature of the substrate (1) corresponds to a longer time. At intermediate temperatures of the indicated range, the annealing time decreases in proportion to the increase in temperature. The width of the terraces (lower terrace (10)) between single monatomic steps (9) evenly distributed over the surface is achieved in the range from 0.1 to 300 μm.

In relation to the above temperature range of 832 ÷ 1410 ° C, used to carry out the stage of creating concentric steps (see Fig. 2a)), after receiving stepped surfaces of the required configuration as a result of thermoelectric annealing, they cease to pass through or through the substrate (1) from the power source (8) electric current, and proceed to the final stage of the formation of a flat atomically smooth surface — preservation of the obtained wide singular surfaces (see Fig. 1d), Fig. 2a)), if required in masks flat surfaces have a diameter up to 100 microns, or increasing the size of the obtained singular broad surfaces with the subsequent saving (see Figure 2B.) - r)), if the required quantity of flat surfaces have a diameter up to 300 microns. In this case, the substrate (1) is cooled under ultra-high vacuum conditions, that is, they also continue to maintain the vacuum of the vacuum chamber (5) with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material into the vacuum during thermoelectric annealing (vacuum level no worse than 10 ^-8 Pa ) The substrate is cooled to a temperature and in a mode in which there is no generation of new monatomic steps, in one case, to room temperature, or, in another case, to a temperature at which, by means of additional thermoelectric annealing, combined with the flow of atoms of the substrate material to its surface and their deposition, an additional increase in size is possible, up to 300 μm in diameter, obtained on a wide singular surface without generating new atomic steps, for example, up to 832 ÷ 1100 ° C and then cooled to room temperature Noah.

The cooling rate is maintained in the first case, preserving the distribution of monoatomic steps obtained as a result of thermoelectric annealing, in the second case, maintaining the distribution of monoatomic steps obtained as a result of thermoelectric annealing, and the distribution of monatomic steps resulting from additional annealing. In quantitative terms, the cooling rate is: when cooling the substrate immediately to room temperature - from 0.1 to 400 ° C / s, when cooling to a temperature of additional thermoelectric annealing, for example, to 832 ÷ 1100 ° C - from 0.1 to 10 ° C / s These temperature regimes of cooling significantly limit the length of migration of adatoms on the terrace (the length of diffusion of adatoms) and prevent the emergence of new monatomic steps.

After the temperature regime is reached, in which the process of the appearance of new monoatomic steps is stopped, but the electromigration of atoms is not stopped in the absence of generation of atomic steps mode, additional annealing can be carried out to achieve the desired size of a flat surface. To carry out additional annealing, the temperature of the substrate, for example, silicon, is set, as mentioned above, in the range of 832–1100 ° С; a source of atomic flux of the substrate material is included, for example, a silicon evaporator, which is a silicon plate fixed in tantalum holders that allow it to pass through It has an electric current and, thus, to form a stream of the required atoms. A constant electric current begins to pass through the silicon wafer to a value sufficient to obtain a silicon flux and deposit it on the substrate at a rate leading to a decrease in the rate of silicon sublimation from the substrate and, as a result, to an increase in the lifetime of adatoms and a significant increase in their migration length. In quantitative terms, the aforementioned deposition rate of atoms of the substrate material on the substrate can be from 0.01 to 0.02 monolayer / sec. At the same time, an increase in the size of the central terrace in diameter up to 100 μm begins to occur in the center of the bottom of the hole on the substrate, if this value is not achieved as a result of the main thermoelectric annealing (see Figure 2). Further, after reaching a size in diameter of 100 μm, the temperature of the substrate can be lowered, remaining equal to the value of the indicated range of 832 ÷ 1100 ° C, while the temperature of the evaporator is proportionally reduced, varying the flux and rate of deposition of atoms of the material of the substrate on the substrate so that the sublimation rate of adatoms from the substrate was constant, corresponding to the case of establishing a quasi-equilibrium surface concentration of adatoms, for example, equal to 0.0001 ÷ 0.002 monolayer / sec. Under these conditions, the substrate is held for a period of time, for example, from 1 to 60 minutes. Moreover, in the center of the bottom of the hole on the substrate there is an increase in the size of the central terrace, and the diameter of the terrace can reach, using the indicated quantitative parameters, from 150 to 200 μm (see Figure 2).

Upon reaching the desired size of the flat surface, the heating of the evaporator and the heating of the substrate are stopped. Next, the substrate is cooled to room temperature.

Thus, with additional annealing, the size d of the lower terrace (10) can be increased to a predetermined size (Fig.2b) - d)), if the latter is not obtained as a result of the main thermoelectric annealing, which causes resistive heating of the substrate material, accompanied by activated sublimation of the atoms of the upper the atomic layer moving along the surface of the steps, with the formation on the periphery of the inner part of the hole, formed by sections of the surface (6) of the substrate (1) deflected in diametrically opposite directions (1) relative to e e of the working surface, clusters of monatomic steps with a high density, with the appearance of single concentric monoatomic steps (9) uniformly distributed around the periphery of the inner part of the well, separated by a singular terrace, with a controlled width (lower terrace (10)), located in the central part holes. After reaching the required size of the singular terrace located in the central part of the hole, the substrate is further cooled to room temperature, stopping the transmission of electric current. Additional thermoelectric annealing is carried out for a period of time sufficient at the selected annealing temperature to achieve the desired size of a wide singular terrace. The specific time interval corresponding to the temperature range of 832 ÷ 1100 ° C is from 1 minute to 10 hours, with the correspondence of a larger time to a lower temperature.

As a result of the implementation of the proposed method, for example, on silicon (111) substrates, surface areas are obtained that do not contain any monoatom steps, reaching sizes in diameter up to 300 microns. The indicated sections of the singular surface of silicon (111), which do not contain a single monoatomic step, have a roughness of not more than 0.4 angstroms (Ra).

As information confirming the possibility of implementing the method with the achievement of the specified technical result, we give the following implementation examples.

Example 1

A hole is formed on the working surface of the substrate (1) of the solid-state material, which consists of sections of the surface of the substrate deflected relative to the working surface of the substrate in diametrically opposite directions, providing opposite directions of the fronts of the atomic steps (surface sections (6) deviated in diametrically opposite directions, see Fig. 1c)) (see Fig. 1a) and b)).

As the substrate of the solid-state material (1), a silicon substrate with a vicinal working surface (111) with a misorientation angle of 0.1 ° is used. The substrate (1) is subjected to ion-beam treatment with Ar ions with an energy of 7 keV for a period of 360 minutes in vacuum with a level sufficient to suppress the effect of residual gases during ion-beam treatment, 10 ^-3 Pa. During processing, the substrate (1) is rotated about an axis directed perpendicular to the working surface of the substrate with a frequency of 100 Hz. The Ar ion beam is directed at an angle to the working surface of the substrate (1), providing the dimensions of the hole necessary to obtain the required area of a flat atomically smooth surface, namely, ensuring the presence of surface sections deviated in diametrically opposite directions with a deflection angle of 15 °.

After receiving the hole as a result of ion-beam treatment, the composition of surface sections (6) deviated in diametrically opposite directions (see Fig. 1c)) conduct thermoelectric annealing of the substrate (1). During thermoelectric annealing, a direct electric current is passed by a value that causes resistive heating of the substrate material (1) to the temperature of activated sublimation of atoms of the upper atomic layer with the movement of monatomic steps on the surface. Moreover, first they carry out preliminary cleaning of the working surface of natural oxide (natural oxide layer (2), see Fig. 1a)) of the substrate material (1) and / or contaminants, annealing, which is the initial stage of thermoelectric annealing. All thermoelectric annealing is carried out in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material (1) in a vacuum characterized by a residual pressure of 10 ^-8 Pa. Electric current is passed parallel to the working surface of the substrate (1). The preliminary annealing, which cleans the working surface of natural oxide of the substrate material (1) and contaminants, which is the initial stage of thermoelectric annealing, is carried out by passing an electric current of a value corresponding to heating to a temperature of 1300 ° C for 10 minutes.

In the subsequent main stage of thermoelectric annealing, an electric current is passed for a time interval of 400 s and at a temperature of 900 ° C, forming a cluster of monoatom steps with a high density, with the characteristic appearance of single concentric monoatom steps evenly distributed along the periphery of the inner part of the well her (9), separated by a singular terrace (lower terrace (10)), with a controlled width located in the central part of the hole (see Fig. 1d) and Fig. 2a)).

After the main stage of thermoelectric annealing, the temperature regime with respect to the substrate (1) is changed, the supply of electric current is stopped and the temperature of the substrate (1) is reduced to room temperature at a rate that preserves the distribution of monatomic steps obtained as a result of thermoelectric annealing, with no generation of new atomic steps, in the final account, preserving the size of the singular terrace in the central part of the hole, namely, at a speed equal to 400 ° C / s in the first second of cooling. The temperature of the substrate is reduced in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material into the vacuum, namely, characterized by a residual pressure of 10 ^-8 Pa.

Example 2

A hole is formed on the working surface of the substrate (1) of the solid-state material, which consists of sections of the surface of the substrate deflected relative to the working surface of the substrate in diametrically opposite directions, providing opposite directions of the fronts of the atomic steps (surface sections (6) deviated in diametrically opposite directions, see Fig. 1c)) (see Fig. 1a) and b)).

As the substrate of the solid-state material (1), a silicon substrate with a vicinal working surface (111) with a misorientation angle of 5 ° is used. The substrate (1) is subjected to ion-beam treatment with Ar ions with an energy of 6.1 keV for a period of 300 minutes in vacuum with a level sufficient to suppress the effect of residual gases during ion-beam treatment, 10 ^-4 Pa. During processing, the substrate (1) is rotated about an axis directed perpendicular to the working surface of the substrate with a frequency of 10 Hz. The Ar ion beam is directed at an angle to the working surface of the substrate (1), providing the dimensions of the hole necessary to obtain the required area of a flat atomically smooth surface, namely, ensuring the presence of surface sections deviated in diametrically opposite directions with a deflection angle of 5 °.

After receiving the hole as a result of ion-beam treatment, the composition of surface sections (6) deviated in diametrically opposite directions (see Fig. 1c)) conduct thermoelectric annealing of the substrate (1). During thermoelectric annealing, an alternating electric current is passed, which causes the resistive heating of the substrate material (1) to the temperature of activated sublimation of the atoms of the upper atomic layer with the movement of monatomic steps on the surface. Moreover, first a preliminary cleaning of the working surface of natural oxide (a layer of natural oxide (2), see Fig. 1a)) is carried out, the substrate material (1) and / or contaminants are annealed, which is the initial stage of thermoelectric annealing. All thermoelectric annealing is carried out in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material (1) in vacuum, characterized by a residual pressure of 5 × 10 ^-8 Pa. Electric current is passed parallel to the working surface of the substrate (1). The preliminary annealing, which cleans the working surface of natural oxide of the substrate material (1) and contaminants, which is the initial stage of thermoelectric annealing, is carried out by passing an electric current of a value corresponding to heating to a temperature of 1410 ° C for 1 minute.

In the subsequent main stage of thermoelectric annealing, an electric current is passed for a time interval of 14000000 s and at a temperature of 832 ° C, forming a cluster of monoatom steps with a high density, with the characteristic appearance of single concentric monoatomic studs uniformly distributed along the periphery of the inner part of the well Enej (9) separated singular terrace (lower terrace (10)), a controlled width situated in the central part of the hole (see. 1D) and 2)).

After the main stage of thermoelectric annealing, the temperature regime with respect to the substrate (1) is changed, the supply of electric current is stopped and the temperature of the substrate (1) is reduced to room temperature at a rate that preserves the distribution of monatomic steps obtained as a result of thermoelectric annealing, with no generation of new atomic steps, in the final account, preserving the size of the singular terrace in the central part of the hole, namely, at a speed equal to 390 ° C / s in the first second of cooling. The temperature of the substrate is reduced in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material into the vacuum, namely, characterized by a residual pressure of 5 × 10 ^-8 Pa.

Example 3

A hole is formed on the working surface of the substrate (1) of the solid-state material, which consists of sections of the surface of the substrate deflected relative to the working surface of the substrate in diametrically opposite directions, providing opposite directions of the fronts of the atomic steps (surface sections (6) deviated in diametrically opposite directions, see Fig. 1c)) (see Fig. 1a) and b)).

A silicon substrate with a vicinal working surface (111) with a misorientation angle of 0 ° 0'20 "is used as a substrate of solid-state material (1). Substrate (1) is subjected to ion beam treatment with Ar ions with an energy of 1 keV for a period of 360 minutes in a vacuum with a level sufficient to suppress the influence of residual gases during ion-beam treatment - 10 ^-3 Pa. During processing, the substrate (1) is rotated relative to the axis directed perpendicular to the working surface of the substrate, with a frequency of 0.1 Hz. Ar direct at an angle m to the working surface of the substrate (1) providing the hole size required to obtain a desired area of a plane atomically smooth surface, namely, providing a deviation in diametrically opposite directions surface portions with a deflection angle of 0 ° 0'10 ".

After receiving the hole as a result of ion-beam treatment, the composition of surface sections (6) deviated in diametrically opposite directions (see Fig. 1c)) conduct thermoelectric annealing of the substrate (1). During thermoelectric annealing, a direct electric current is passed by a value that causes resistive heating of the substrate material (1) to the temperature of activated sublimation of atoms of the upper atomic layer with the movement of monatomic steps on the surface. Moreover, first they carry out preliminary cleaning of the working surface of natural oxide (natural oxide layer (2), see Fig. 1a)) of the substrate material (1) and / or contaminants, annealing, which is the initial stage of thermoelectric annealing. All thermoelectric annealing is carried out in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material (1) in vacuum, characterized by a residual pressure of 2 × 10 ^-8 Pa. Electric current is passed parallel to the working surface of the substrate (1). The preliminary annealing, which cleans the working surface of natural oxide of the substrate material (1) and contaminants, which is the initial stage of thermoelectric annealing, is carried out by passing an electric current of a value corresponding to heating to a temperature of 1250 ° C for 15 minutes.

In the subsequent main stage of thermoelectric annealing, an electric current is passed for a period of 8 s and at a temperature of 1410 ° C, forming a cluster of monoatom steps with high density, with the characteristic appearance of single concentric monoatom steps evenly distributed around the periphery of the inner part of the well D (9) separated singular terrace (lower terrace (10)), a controlled width situated in the central part of the hole (see. 1D) and 2)).

After the main stage of thermoelectric annealing, the temperature regime with respect to the substrate (1) is changed, the supply of electric current is stopped and the temperature of the substrate (1) is reduced to room temperature at a rate that preserves the distribution of monatomic steps obtained as a result of thermoelectric annealing, with no generation of new atomic steps, in the final account, preserving the size of the singular terrace in the central part of the hole, namely, at a speed equal to 385 ° C / s in the first second of cooling. The temperature of the substrate is reduced in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material into the vacuum, namely, characterized by a residual pressure of 2 × 10 ^-8 Pa.

Example 4

A hole is formed on the working surface of the substrate (1) of the solid-state material, which consists of sections of the surface of the substrate deflected relative to the working surface of the substrate in diametrically opposite directions, providing opposite directions of the fronts of the atomic steps (surface sections (6) deviated in diametrically opposite directions, see Fig. 1c)) (see Fig. 1a) and b)).

As the substrate of the solid-state material (1), a silicon substrate with a working surface (111) is used. The substrate (1) is subjected to ion-beam treatment with Ar ions with an energy of 7 keV for a period of 360 minutes in vacuum with a level sufficient to suppress the effect of residual gases during ion-beam treatment, 10 ^-3 Pa. During processing, the substrate (1) is rotated about an axis directed perpendicular to the working surface of the substrate with a frequency of 90 Hz. The Ar ion beam is directed at an angle to the working surface of the substrate (1), providing the dimensions of the hole necessary to obtain the required area of a flat atomically smooth surface, namely, ensuring the presence of surface sections deviated in diametrically opposite directions with a deflection angle of 14 °.

After receiving the hole as a result of ion-beam treatment, the composition of surface sections (6) deviated in diametrically opposite directions (see Fig. 1c)) conduct thermoelectric annealing of the substrate (1). During thermoelectric annealing, a direct electric current is passed by a value that causes resistive heating of the substrate material (1) to the temperature of activated sublimation of atoms of the upper atomic layer with the movement of monatomic steps on the surface. Moreover, first a preliminary cleaning of the working surface of natural oxide (a layer of natural oxide (2), see Fig. 1a)) is carried out, the substrate material (1) and / or contaminants are annealed, which is the initial stage of thermoelectric annealing. All thermoelectric annealing is carried out in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material (1) in a vacuum characterized by a residual pressure of 10 ^-8 Pa. Electric current is passed parallel to the working surface of the substrate (1). The preliminary annealing, which cleans the working surface of natural oxide of the substrate material (1) and contaminants, which is the initial stage of thermoelectric annealing, is carried out by passing an electric current of a value corresponding to heating to a temperature of 1350 ° C for 8 minutes.

In the subsequent main stage of thermoelectric annealing, an electric current is passed for a period of 380 s and at a temperature of 910 ° C, forming a cluster monoatom steps with a high density, with the characteristic appearance of single concentric monoatom steps evenly distributed along the periphery of the inner part of the well her (9), separated by a singular terrace (lower terrace (10)), with a controlled width located in the central part of the hole (see Fig. 1d) and Fig. 2a)).

After the main stage of thermoelectric annealing, the temperature regime with respect to the substrate (1) is changed, the supply of electric current is stopped and the temperature of the substrate (1) is reduced to room temperature at a rate that preserves the distribution of monatomic steps obtained as a result of thermoelectric annealing, with no generation of new atomic steps, in the final account, preserving the size of the singular terrace in the central part of the hole, namely, at a speed equal to 395 ° C / s in the first second of cooling. The temperature of the substrate is reduced in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material into the vacuum, namely, characterized by a residual pressure of 10 ^-8 Pa.

Example 5

A hole is formed on the working surface of the substrate (1) of the solid-state material, which consists of sections of the surface of the substrate deflected relative to the working surface of the substrate in diametrically opposite directions, providing opposite directions of the fronts of the atomic steps (surface sections (6) deviated in diametrically opposite directions, see Fig. 1c)) (see Fig. 1a) and b)).

As the substrate of the solid-state material (1), a silicon substrate with a vicinal working surface (111) with a misorientation angle of 0.1 ° is used. The substrate (1) is subjected to ion-beam treatment with Ar ions with an energy of 7 keV for a period of 360 minutes in vacuum with a level sufficient to suppress the effect of residual gases during ion-beam treatment, 10 ^-3 Pa. During processing, the substrate (1) is rotated about an axis directed perpendicular to the working surface of the substrate with a frequency of 100 Hz. The Ar ion beam is directed at an angle to the working surface of the substrate (1), providing the dimensions of the hole necessary to obtain the required area of a flat atomically smooth surface, namely, ensuring the presence of surface sections deviated in diametrically opposite directions with a deflection angle of 15 °.

After receiving the hole as a result of ion-beam treatment, the composition of surface sections (6) deviated in diametrically opposite directions (see Fig. 1c)) conduct thermoelectric annealing of the substrate (1). During thermoelectric annealing, a direct electric current is passed by a value that causes resistive heating of the substrate material (1) to the temperature of activated sublimation of atoms of the upper atomic layer with the movement of monatomic steps on the surface. Moreover, first a preliminary cleaning of the working surface of natural oxide (a layer of natural oxide (2), see Fig. 1a)) is carried out, the substrate material (1) and / or contaminants are annealed, which is the initial stage of thermoelectric annealing. All thermoelectric annealing is carried out in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material (1) in a vacuum characterized by a residual pressure of 10 ^-8 Pa. Electric current is passed parallel to the working surface of the substrate (1). The preliminary annealing, which cleans the working surface of natural oxide of the substrate material (1) and contaminants, which is the initial stage of thermoelectric annealing, is carried out by passing an electric current of a value corresponding to heating to a temperature of 1300 ° C for 10 minutes.

In the subsequent main stage of thermoelectric annealing, an electric current is passed for a time interval of 400 s and at a temperature of 900 ° C, forming a cluster of monoatom steps with a high density, with the characteristic appearance of single concentric monoatom steps evenly distributed along the periphery of the inner part of the well her (9), separated by a singular terrace (lower terrace (10)), with a controlled width located in the central part of the hole (see Fig. 1d) and Fig. 2a)).

After the main stage of thermoelectric annealing, the temperature regime with respect to the substrate (1) is changed, the supply of electric current is limited and the temperature of the substrate (1) is limited at a rate that preserves the distribution of monoatomic steps obtained as a result of thermoelectric annealing, with no generation of new atomic steps, namely, with at a rate of 10 ° C / s to a temperature which is characterized by the absence of generation of new atomic steps, but with respect to which the electromigration of atoms has not stopped, namely, to temperatures s equal to 850 ° C. Then, through an additional step of thermoelectric annealing at the indicated temperature, with the flow of atoms of the substrate material onto the substrate, increasing the length of electromigration of atoms, namely, the flow providing the deposition rate of atoms on the substrate surface of 0.02 monolayer / s, the size of the resulting singular terrace in the central parts of the hole, annealing for a period of time sufficient to obtain the desired size, namely, for a period of time equal to 4 hours. Then it is cooled to room temperature at a rate that preserves the distribution of monatomic steps obtained as a result of additional thermoelectric annealing, with no generation of new atomic steps, and ultimately preserves the size of the additionally enlarged singular terrace in the central part of the well, namely, at a speed of 400 ° C / s The temperature of the substrate is reduced in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material into the vacuum, namely, characterized by a residual pressure of 10 ^-8 Pa.

Example 6

A hole is formed on the working surface of the substrate (1) of the solid-state material, which consists of sections of the surface of the substrate deflected relative to the working surface of the substrate in diametrically opposite directions, providing opposite directions of the fronts of the atomic steps (surface sections (6) deviated in diametrically opposite directions, see Fig. 1c)) (see Fig. 1a) and b)).

As the substrate of the solid-state material (1), a silicon substrate with a vicinal working surface (111) with a misorientation angle of 0.09 ° is used. The substrate (1) is subjected to ion beam treatment with Ar ions with an energy of 7 keV for a period of 1 minute in vacuum with a level sufficient to suppress the effect of residual gases during ion beam treatment, 10 ^-4 Pa. During processing, the substrate (1) is rotated about an axis directed perpendicular to the working surface of the substrate with a frequency of 100 Hz. The Ar ion beam is directed at an angle to the working surface of the substrate (1), providing the dimensions of the hole necessary to obtain the required area of a flat atomically smooth surface, namely, ensuring the presence of surface sections deviated in diametrically opposite directions with a deflection angle of 15 °.

After receiving the hole as a result of ion-beam treatment, the composition of surface sections (6) deviated in diametrically opposite directions (see Fig. 1c)) conduct thermoelectric annealing of the substrate (1). During thermoelectric annealing, a direct electric current is passed by a value that causes resistive heating of the substrate material (1) to the temperature of activated sublimation of atoms of the upper atomic layer with the movement of monatomic steps on the surface. Moreover, first they carry out preliminary cleaning of the working surface of natural oxide (natural oxide layer (2), see Fig. 1a)) of the substrate material (1) and / or contaminants, annealing, which is the initial stage of thermoelectric annealing. All thermoelectric annealing is carried out in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material (1) in vacuum, characterized by a residual pressure of 2 × 10 ^-8 Pa. Electric current is passed parallel to the working surface of the substrate (1). The preliminary annealing, which cleans the working surface of natural oxide of the substrate material (1) and contaminants, which is the initial stage of thermoelectric annealing, is carried out by passing an electric current of a value corresponding to heating to a temperature of 1300 ° C for 10 minutes.

In the subsequent main stage of thermoelectric annealing, an electric current is passed for a time interval of 400 s and at a temperature of 900 ° C, forming a cluster of monoatom steps with a high density, with the characteristic appearance of single concentric monoatom steps evenly distributed along the periphery of the inner part of the well her (9), separated by a singular terrace (lower terrace (10)), with a controlled width located in the central part of the hole (see Fig. 1d) and Fig. 2a)).

After the main stage of thermoelectric annealing, the temperature regime with respect to the substrate (1) is changed, the supply of electric current is limited and the temperature of the substrate (1) is limited at a rate that preserves the distribution of monoatomic steps obtained as a result of thermoelectric annealing, with no generation of new atomic steps, namely, with at a rate of 0.1 ° C / s, to a temperature which is characterized by the absence of generation of new atomic steps, but with respect to which the electromigration of atoms has not stopped, namely, to the temperature ry equal to 832 ° С. Further, by means of an additional step of thermoelectric annealing at the indicated temperature, with the flow of atoms of the substrate material onto the substrate, increasing the length of electromigration of atoms, namely, the flow providing the deposition rate of atoms on the substrate surface of 0.01 monolayer / s, the size of the resulting singular terrace is further increased by the central part of the hole, annealing for a period of time sufficient to obtain the desired size, namely, for a period of time equal to 10 hours. Then it is cooled to room temperature at a rate that preserves the distribution of monatomic steps obtained as a result of additional thermoelectric annealing, with no generation of new atomic steps, and ultimately preserves the size of the additionally enlarged singular terrace in the central part of the well, namely, at a speed of 300 ° C / s The temperature of the substrate is reduced in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material into the vacuum, namely, characterized by a residual pressure of 2 × 10 ^-8 Pa.

Example 7

A hole is formed on the working surface of the substrate (1) of the solid-state material, which consists of sections of the surface of the substrate deflected relative to the working surface of the substrate in diametrically opposite directions, providing opposite directions of the fronts of the atomic steps (surface sections (6) deviated in diametrically opposite directions, see Fig. 1c)) (see Fig. 1a) and b)).

As the substrate of the solid-state material (1), a silicon substrate with a vicinal working surface (111) with a misorientation angle of 0.1 ° is used. The substrate (1) is subjected to ion-beam treatment with Ar ions with an energy of 7 keV for a period of 360 minutes in vacuum with a level sufficient to suppress the effect of residual gases during ion-beam treatment, 10 ^-3 Pa. During processing, the substrate (1) is rotated about an axis directed perpendicular to the working surface of the substrate with a frequency of 100 Hz. The Ar ion beam is directed at an angle to the working surface of the substrate (1), providing the dimensions of the hole necessary to obtain the required area of a flat atomically smooth surface, namely, ensuring the presence of surface sections deviated in diametrically opposite directions with a deflection angle of 15 °.

After receiving the hole as a result of ion-beam treatment, the composition of surface sections (6) deviated in diametrically opposite directions (see Fig. 1c)) conduct thermoelectric annealing of the substrate (1). During thermoelectric annealing, a direct electric current is passed by a value that causes resistive heating of the substrate material (1) to the temperature of activated sublimation of atoms of the upper atomic layer with the movement of monatomic steps on the surface. Moreover, first they carry out preliminary cleaning of the working surface of natural oxide (natural oxide layer (2), see Fig. 1a)) of the substrate material (1) and / or contaminants, annealing, which is the initial stage of thermoelectric annealing. All thermoelectric annealing is carried out in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material (1) in a vacuum, characterized by a residual pressure of 6 × 10 ^-8 Pa. Electric current is passed parallel to the working surface of the substrate (1). The preliminary annealing, which cleans the working surface from natural oxide of the substrate material (1) and contaminants, which is the initial stage of thermoelectric annealing, is carried out by passing an electric current of a value corresponding to heating to a temperature of 1310 ° C for 11 minutes.

In the subsequent main stage of thermoelectric annealing, an electric current is passed for a period of time of 10 s and at a temperature of 1400 ° C, forming a cluster of monoatom steps with a high density, with the characteristic appearance of single concentric monoatom steps evenly distributed along the periphery of the inner part of the well her (9), separated by a singular terrace (lower terrace (10)), with a controlled width located in the central part of the hole (see Fig. 1d) and Fig. 2a)).

After the main stage of thermoelectric annealing, the temperature regime with respect to the substrate (1) is changed, the supply of electric current is limited and the temperature of the substrate (1) is limited at a rate that preserves the distribution of monoatomic steps obtained as a result of thermoelectric annealing, with no generation of new atomic steps, namely, with at a rate of 9 ° C / s, to a temperature which is characterized by the absence of generation of new atomic steps, but with respect to which the electromigration of atoms has not stopped, namely, to temperatures s equal to 1100 ° C. Further, by means of an additional step of thermoelectric annealing at the indicated temperature, with the flow of atoms of the substrate material onto the substrate, increasing the length of the electromigration of atoms, namely, first, a stream providing the deposition rate of atoms on the substrate surface of 0.02 monolayer / s, thereby achieving a terrace size in diameter 100 μm, and then, reducing the flow, to ensure a deposition rate of atoms on the substrate surface of 0.018 monolayer / s, and lowering the temperature of the substrate to 900 ° C, further increase the size of the obtained of a singular terrace in the central part of the hole, annealing for a period of time sufficient to obtain the desired size, namely, for a period of time equal to 1 minute. Then it is cooled to room temperature at a rate that preserves the distribution of monatomic steps obtained as a result of additional thermoelectric annealing, with no generation of new atomic steps, and ultimately preserves the size of the additionally enlarged singular terrace in the central part of the well, namely, at a speed of 350 ° C / s The temperature of the substrate is reduced in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the material of the substrate into vacuum, namely, characterized by a residual pressure of 6 × 10 ^-8 Pa.

By the method described in this example implementation, a singular terrace is formed, as shown in the photographs in FIG. 3. Its size is 200 μm × 160 μm (see Fig. 3, position (10) in Fig. 3b)). The terrace is limited by the accumulation of closely spaced monatomic steps separated by narrow terraces (11) (see Fig. 3a) and b)).

Claims (9)

1. The method of forming a flat smooth surface of a solid-state material is that thermoelectric annealing of the substrate is carried out, characterized in that before conducting thermoelectric annealing on the working surface of the substrate of the solid-state material, a hole is formed consisting of portions of the surface of the substrate deflected diametrically opposite to the working surface of the substrate directions providing opposite directions of the fronts of atomic steps during thermoelectric annealing they dispense direct or alternating electric current with a value causing resistive heating of the substrate material to the temperature of activated sublimation of the atoms of the upper atomic layer with movement along the surface of the monatomic steps, and first annealing is performed, which cleans the working surface of the natural oxide of the substrate material and / or contaminants, which is the initial stage thermoelectric annealing, then carry out the main stage of thermoelectric annealing or conduct the main stage of thermoelectric of annealing and an additional step of thermoelectric annealing, all thermoelectric annealing is carried out in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material into vacuum, an electric current is passed parallel to the working surface of the substrate, over a period of time and under the temperature regime, forming the periphery of the inner part of the well, formed by sections of the surface of the substrate deflected in diametrically opposite directions relative to its working surface a cluster of monoatom steps with a high density, with the characteristic appearance of single concentric monoatom steps evenly distributed along the periphery of the inner part of the well, separated by a singular terrace, with a controlled width located in the central part of the well, after the main stage of thermoelectric annealing, the temperature regime with respect to the substrate is changed , the supply of electric current is stopped and the temperature of the substrate is reduced to room temperature at a speed that preserves the resulting e the main stage of thermoelectric annealing, the distribution of monatomic steps, with the lack of generation of new atomic steps, ultimately preserving the size of the singular terrace in the central part of the hole, or after the main stage of thermoelectric annealing, the supply of electric current is limited and the substrate temperature is reduced at a rate that preserves the obtained as a result of the main stage of thermoelectric annealing, the distribution of monatomic steps, with the absence of the generation of new atoms of many steps, to a temperature which is characterized by the absence of generation of new atomic steps, but with respect to which the electromigration of atoms has not been stopped, and through an additional step of thermoelectric annealing at the indicated temperature, with the flow of atoms of the substrate material onto the substrate, increasing the length of atomic electromigration, the size of the singular terrace obtained in the main part of the thermoelectric annealing in the central part of the hole, annealing during the gap a belt sufficient to obtain the required size, and then cooled to room temperature at a rate that preserves the distribution of monatomic steps obtained as a result of an additional step of thermoelectric annealing, with no generation of new atomic steps, ultimately preserves the size of the additionally enlarged singular terrace in the central part of the hole . 2. The method according to claim 1, characterized in that a silicon substrate with a working surface orientation (111) or a silicon substrate with a vicinal working surface (111) with a misorientation angle of 0 ° 0'20 "to 5 °. 3. The method according to claim 1, characterized in that a hole is formed consisting of portions of the substrate surface deflected relative to the working surface of the substrate in diametrically opposite directions, providing opposite directionality of the fronts of the atomic steps, in that the substrate is subjected to ion beam treatment with Ar ions energy from 1 keV to 7 for a time of from 1 to 360 minutes in a vacuum at a level sufficient to inhibit the effect of residual gas during the ion-beam treatment, namely not more than 10 ^-3 Pa at during processing, the substrate is rotated about an axis directed perpendicular to the working surface of the substrate, with a frequency of 0.1 to 100 Hz, the ion beam is directed at an angle to the working surface of the substrate, providing the dimensions of the hole necessary to obtain the required area of a flat atomically smooth surface, namely, providing the presence of surface sections deviated in diametrically opposite directions with an angle of deviation from 0 ° 0'10 "to 15 °. 4. The method according to claim 1, characterized in that the thermoelectric annealing is carried out in vacuum with a level sufficient to suppress the influence of residual gases and the release of atoms of the substrate material into the vacuum, namely, characterized by a residual pressure of not more than 10 ^-8 Pa. 5. The method according to claim 1, characterized in that annealing is carried out preliminary, cleaning the working surface of natural oxide of the substrate material and / or contaminants, which is the initial stage of thermoelectric annealing, passing an electric current of a value corresponding to heating to a temperature from 1250 ° C to 1410 ° C for a minute or more. 6. The method according to claim 1, characterized in that the main stage of thermoelectric annealing is carried out, in which direct or alternating electric current is passed by a value causing resistive heating of the substrate material to the temperature of activated sublimation of atoms of the upper atomic layer with the movement of monoatom steps along the surface, electric current pass parallel to the working surface of the substrate, over a period of time and under temperature conditions, forming on the periphery of the inner part of the hole formed by the deviation areas of the substrate surface relative to its working surface in diametrically opposite directions, the accumulation of monoatom steps with a high density, with the appearance of single concentric monoatom steps evenly distributed around the periphery of the well, separated by a singular terrace, with a controlled width located in the central part of the well, and namely, to the temperature of the temperature regime from 832 ° C to 1410 ° C and the time interval from 8 to 14000000 s, with less correspondence erature annealing time greater heating of the substrate, with decreasing values at intermediate temperature range of said annealing time proportional to the increase in temperature. 7. The method according to claim 1, characterized in that after the main stage of thermoelectric annealing, the temperature regime with respect to the substrate is changed, the supply of electric current is stopped and the temperature of the substrate is reduced to room temperature at a rate that preserves the distribution of monatomic steps obtained as a result of thermoelectric annealing, with no generation of new atomic steps, which ultimately preserves the size of the singular terrace in the central part of the hole, namely, at a speed of 0.1 to 400 ° C / s. 8. The method according to claim 1, characterized in that after the main stage of thermoelectric annealing, the temperature regime with respect to the substrate is changed, the supply of electric current is limited and the temperature of the substrate is reduced at a rate that preserves the distribution of monatomic steps obtained as a result of thermoelectric annealing, with no generation of new atomic steps, namely from 0.1 to 10 ° C / s, to a temperature which is characterized by the absence of generation of new atomic steps, but with respect to which the electromigration of atoms is not stopped, but to a temperature equal to 832 ° С to 1100 ° С, and an additional thermoelectric annealing step is carried out, at which direct or alternating electric current is passed by a value that causes resistive heating of the substrate material to the temperature of activated sublimation of atoms of the upper atomic layer with the movement of monatomic steps on the surface , an electric current is passed parallel to the working surface of the substrate, over a period of time and under temperature conditions, forming an image on the periphery of the inner part of the hole The surface of the substrate deviated in diametrically opposite directions relative to its working surface is an accumulation of monoatom steps with a high density, with the characteristic appearance of single concentric monoatom steps evenly distributed around the periphery of the well, separated by a singular terrace, with a controlled width located in the central part of the well, through an additional step of thermoelectric annealing at the specified temperature, with a flow of at ohms of the substrate material on the substrate, increasing the length of the electromigration of atoms, namely, the flow providing the deposition rate of atoms on the surface of the substrate from 0.01 to 0.02 monolayer / s, further increase the size of the resulting singular terrace in the Central part of the hole, annealing for a period of time sufficient to obtain the required size, namely, for a period of time from 1 minute to 10 hours, with a longer time corresponding to a lower temperature of additional thermoelectric annealing, and then cooling to room temperature at a rate that preserves the distribution of monatomic steps obtained as a result of additional thermoelectric annealing, with the absence of generation of new atomic steps, and ultimately preserves the size of the additionally enlarged singular terrace in the central part of the well, namely, at a speed of 10 to 400 ° C / s 9. The method according to claim 7 or 8, characterized in that lowering the temperature of the substrate or lowering the temperature of the substrate and performing an additional step of thermoelectric annealing with a further decrease, the temperature of the substrate to room temperature is carried out in vacuum with a level sufficient to suppress the effect of residual gases and the release of atoms of the material substrate in a vacuum, namely, characterized by a residual pressure of not more than 10 ^-8 Pa.

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