RU1484191C - Method of producing monocrystal films of semiconducting materials - Google Patents

Description

() December 15, 92 Bull. K 6 (21) 4237766/25 22) 04.29.87

(71) Institute of Radio Engineering and Electrical Engineering, USSR Academy of Sciences

(72) Yu.V. Gulev, I.M. Kotelnsky, V.A. Lueanov and S.A. Tarakanova

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(56) Mender E. et al. Optical properties of GaSb-AlSb superlattices.

J. Vac. Sci. Technol. 1983, -BI (2), p. li 2- 54.

Taked T. et al. Growth of ZnS / ZnTe and ZnSe / ZnTe superlattices by molecular beam epitaxy and atomic layer epitaxy. Surface Sci, 1986, N 174, p. 548-549.

(54) METHOD FOR PRODUCING MULTI-CRYSTAL FILMS OF SEMICONDUCTOR MATERIALS

(57) The invention relates to a technology for producing thin (several monospots) semiconductor films for solid-state microelectronic devices and can be used, in particular, to produce such promising semiconductor structures as superunits. The purpose of the invention is to increase the uniformity of the film in terms of its composition, thickness, surface area and batch while increasing

process productivity. Precipitation of the components is carried out in spatially separated zones of sediment-1 day. The substrate grows at a constant speed V4 (l-Vp) hM, where 1 is the beam size in the direction of movement of the substrate; Vp is the growth rate of the deposited substance on the substrate of a given crystallographic orientation at a given deposition temperature and flux density; hM - crowd-sh -1 monolayer of the precipitated substance. The application of the next monolayer is carried out after a period of time no less than the time of desorption of physically adsorbed atoms on the working surface of the substrate at a given deposition temperature. To enhance the surface diffusion of chemisorbed atoms during the movement of the substrate outside the flow of the deposited substance, the deposited film is exposed to radiation with a wavelength equal to (h-cJ / E Л (hc) / E0, where h is the Planck constant; c is the speed of light in vacuum ; E. - the activation energy of surface diffusion of chemisorbed atoms on the surface of the substrate of a given crystallographic orientation; Pr - the energy of desorption of physically adsorbed atoms.

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The invention relates to a technology for producing monocrystal films of molybdenum materials for i Rt-rhttp microelectronic devices and has been used, in particular, for the manufacture of superguns.

The purpose of the invention is to increase the uniformity of the film according to the technical composition, by thickness, by flooding day

substrates and in the batch while increasing the productivity of the process.

The essence of the method consists in the sequential deposition of monolayers of components of the film material in spatially separated deposition zones, the deposition of the next monolayer being carried out after a period of time not less than the time of desorption of physically adsorbed atoms on the working surface of the substrate at a given deposition temperature.

Under the indicated deposition conditions, it became possible to carry out layered molecular beam epitakeia and reproducibly obtain uniform stoichiometric composition, degrees of crystalline perfection and film thickness over the entire area of not only one substrate, but the entire series of substrates in one cycle.

This method made it possible to abandon the damper system, the synchronization unit of their operation mode and the control computer, which greatly simplifies the design of the installation and improves productivity.

The method makes it possible to arrange successively the sources of components of the deposited substance, sources of dopants, ion sources for cleaning the working surface of the substrate and film, sources of exposure to each monolayer by radiation, which enhances the surface migration of chemisorbed atoms and accelerates the desorption of physically adsorbed atoms

-14841914

can be calculated or experimentally determined by measuring the time dependence of the flux density of desorbed atoms from the surface of the substrate at a given deposition temperature. The maximum time between successive deposition of component monolayers is limited

IQ process of contaminating the surface of the deposited monolayer with a residual vacuum, as well as a decrease in plant productivity with an increase in the exposure time between successive deposition of monolayers.

The deposition temperature is chosen to be higher than the so-called critical temperature, above which the adhesion coefficient becomes less than unity and the build-up of the deposition pattern is possible. The epitaxial rate is determined. Experimental rate25

thirty

35

40

blowing way. A film of the component material is deposited on a substrate at room temperature. Then the substrate is gradually heated in high vacuum and the temperature dependence of the Auger signal intensity on the film surface is removed. The Auger signal intensity in a certain temperature range of the substrate practically ceases to change, which means the completion of the desorption of weakly bound component atoms and the establishment of a stable surface formed by chemisorbed atoms. Similarly, the temperature range of obtaining a stable surface for each of the components separately on a given substrate is determined. The deposition temperature of the substance is selected from the Overlap area of possible temperatures to obtain a stable surface for each component.

The speed of movement of the substrate is chosen so that it provides at a given deposition temperature and deposition flux density on the working surface of the substrate the number of atoms slightly greater than or equal to the amount required to form one monolayer of chemisorbed atoms. A significant decrease in the speed of movement of the substrate is “undesirable because of a decrease in productivity and excessive consumption of materials.”

The minimum time between successive deposition of two monolayers, is determined by the time of desorption of physically adsorbed atoms on the working surface of the substrate at a given deposition temperature, which

 possibly no slepitaxial Experimental pace5

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5

0

5

,

blowing way. A film of the component material is deposited on a substrate at room temperature. Then the substrate is gradually heated in high vacuum and the temperature dependence of the Auger signal intensity on the film surface is removed. The Auger signal intensity in a certain temperature range of the substrate practically ceases to change, which means the completion of the desorption of weakly bound component atoms and the establishment of a stable surface formed by chemisorbed atoms. Similarly, the temperature range of obtaining a stable surface is determined for each of the components separately on a given substrate. The deposition temperature of the substance is selected from the Overlap area of possible temperatures to obtain a stable surface for each component.

The film growth rate of the component is determined as follows. A film is deposited onto a substrate at a given deposition temperature and component flux density. Then, by measuring its thickness and dividing this thickness by the deposition time, a growth rate value is obtained. More specifically, the growth rate is determined by the period of synchronous oscillations of the intensity and width of the electron diffraction reflex from the surface of the frozen film. The oscillation period is equal to the build time of one component monolayer.

With a chosen width of 1, the size of the beam was determined in the direction of motion of the substrate, the speed of movement of the substrate is determined from the formula

v Uch

where vp is the growth rate}

Bc is the thickness of the monolayer. In order to enhance the surface diffusion of chemisorbed atoms of a component and to accelerate the desorption of physically adsorbed atoms, and therefore, to improve the degree of crystalline perfection of the film, in the intervals between the deposition of monolayers, radiation with a wavelength is applied to the surface of the growing film

h-s / / h s

 YOG§

where h is Planck's constant;

c is the speed of light in vacuum; E is the activation energy of surface diffusion of a chemisorbed atom on a substrate surface of a given crystallographic orientation; EZ - energy of desorption physically

adsorbed atom. The radiation energy is chosen such that chemisorbed atoms located outside the bottom of the potential surface topography, having absorbed a quantum of light with a selected wavelength, are able to occupy positions due to surface diffusion corresponding to the minimum potential energy, i.e. occupy positions corresponding to the best crystalline perfection of the structure. The radiation power density W is estimated from h.c L

conditions W

N

where N

tf.1f -U cm is the surface density of atoms, and in the order of magnitude is Y v 1-x- (Gg-10 J / cmg. The radiation wavelength is determined for each component individually. Example 1. Deposition of a single-crystal CdTe film wire t on CdTe substrates of orientation (PO) in an ultrahigh-vacuum installation of molecular beam epitaxy.

The installation comprises a pumping system, a working chamber, in which a drum-substrate-underrunner with a diameter of 100 mm and a height of 30 mm is placed. A different source for cleaning the substrates, a source of Cd molecular beam and a source of Te molecular beams are sequentially placed around the chamber perimeter. The effusion cells Cd and Te are located opposite each other on opposite sides of the drum. The gap width for Te vapor is 10 mm. Slit length 1 # JQ 20 mm. Slots are located at a distance of -; 1 mm from the working surface of the substrates.

CdTe Single Crystal Substrates

orientation (BUT) size Ixi cmg in

5 quantity of 20 pieces are fixed on

outer side of the drum. The working chamber is pumped out to a maximum vacuum of 10 Pa, an argon flow is introduced up to 10 Pa, rotation is turned on

0 drum at a speed of 12 r / h and yklyu-. an ion source is used to clean the working surface of the substrates. The operating parameters of the ion source: U "l KB, I & 0.2 A, the diameter of the ion beam

5 50 mm, slit width 20 mm, slit length 20 mm. The cleaning is carried out for (30 minutes. Then the ion source is turned off, the rotation of the drum is stopped and the working chamber is pumped out to

0. 10 Pa. They include heating the substrates, heating them to a temperature of 600 K, anneal for 30 mph, after which the temperature is reduced to a deposition temperature of 540 K.

g The Cd and Te effusion cells, which are closed by flaps, are heated to temperatures of 580 K and 670 K, respectively, and held for 15 minutes to stabilize their operating modes. After

To warm up the effusion cells, the drum rotates at a speed of 12 rpm, the shutters are opened, and Cd and Te monolayers are sequentially deposited through the slits.

5 Under these conditions, 120 monolayers of the CdTe compound are deposited in 20 cycles on a single substrate in 10 hours.

The obtained CdTe films with a thickness of 1000 A had a smooth specular surface.

Example 2. The deposition of a single-crystal GaAs film is carried out on GaAs substrates of (100) orientation. Sources of Ga and As atoms are

e gas flows are trimethyl gallium (TMG) and ersine (AslI), respectively. Optical radiation sources are installed between the TMG and AsH3 gas inlets to enhance the surface diffusion of chemisorbed Ga and As atoms. The substrates are made of a GaAs single crystal of (100) orientation. The diameter of the sub-pads is 15 mm, the number of substrates is 15 pieces.

The deposition is carried out analogously to the example under the following modes: deposition temperature 870 K, gas inlet speeds 7 W Pa l / s- (for ArH4) and 1, Pa l / s (for TMG), slit width for arsine flow 2 mm , for a TMG flux 1mhz -5 mm, slit length 20 mm, optical radiation operating parameters: wavelength for atoms G - 0.8 μm, for AzALЈ i atoms 2.5 μm, power density - for Ga atoms 10 J / cm a, for As atoms, Md5 J / cm%, the width of the slits of the optical radiation is 20 mm, the length of the slits is 20 mm.

Under the indicated conditions, the drum rotational speed is 20 rpm. In one cycle, 200 monolayers of the compound are deposited on t5 substrates in 10 hours

GaAs.

Example 3. Obtaining a ZnSe-ZnTe superlattice was carried out on GaAs substrates of orientation (lOQj, size 1 5 cm 8 - in the amount of 30 pieces of molecular beams. Sources of molecular beams were located around the perimeter of the working chamber in the following sequence: first vapor — source Zn — source Se; second pa - ipa - source Zn - source Te, etc. A total of 5 pairs of sources were established .1 Deposition was carried out similarly to example} under the following conditions: diameter of drum-podpozhkoderzhatel - 200 mm, height - 30 mm, deposition temperature 280 C, the temperature of the sources culinary beams: T% - 580 K, T Se 430 K, TG (670 K, width of source slits: 1pn-5 mm, $ 1 in 10 mm, ° 5 mm, lfe 10 mm, slit length 20 mm. The drum rotational speed under these conditions was 6 rpm. The resulting structure of 100 monolayers had a smooth surface.

Thus, in comparison with the known method, this method makes it possible to reproducibly produce monocrystalline films of various semiconductor compounds with a high degree of uniformity in stoichiometric composition and more coherent in crystal structure.

In addition, the use of a continuous mode of operation of sources and uniform movement of substrates instead of using flow interruption devices with synchronization units for their operation modes significantly simplifies the design of the installation and helps to increase its productivity.

Claims (2)

The claims . A method for producing mono-hystalic films of semiconductor materials by the method of layer-by-layer molecular beam epitaxy, which includes heating the substrate in vacuum to the deposition temperature and sequential deposition of monolayer material components by supplying a material flow to the working surface of the substrate, which distinguishes both that, in order to increase the uniformity of the film in stoichiometric composition and thickness over the substrate area and in the batch while increasing the productivity of the process, the deposition of the components of the wire given in spatially separated deposition zones, and the substrate is rotated at a constant speed v PM where 1 is the beam size in the direction substrate movements; Vp is the growth rate of the deposited substance on the substrate of a given crystallographic orientation at a given temperature of deposition and flux density; 4 bc - the given thickness of the monolayer the deposited substance, and the deposition of each subsequent monolayer is carried out after a period of time not less than the time of desorption of physically adsorbed atoms on the working surface of the substrate. 2. The method of pop. 1, characterized in that during the movement of the substrate outside the deposition zone, the film is exposed to radiation with a wavelength of D, and 1 l l h-c Ed ES where is Planck's constant; c is the speed of light in vacuum; E4 - activation energy of surface diffusion of chemically absorbed atoms on the surface 9I48419IU substrate of a given crystal-E5 - energy of desorption physically graphic orientation; adsorbed atoms.