RU2671349C1 - Method of producing monocrystalline sic - Google Patents

Abstract

FIELD: electrical engineering.SUBSTANCE: invention relates to microelectronics and relates to the technology of producing monocrystalline SiC – a widespread material, used to make integrated circuits. Method of producing monocrystalline SiC involves sublimation of a source of SiC placed in a crucible onto a plate of a seed mono crystal SiC, wherein the growth stage of mono crystal SiC is carried out in atmosphere of a gas mixture of inert gas and hydrogen, while in growth chamber is placed having a hole in the bottom of the crucible by its installation on the holder of the crucible having axial through hole, in such a way that the holes in the bottom of the crucible and in the holder form a channel for passage of gases, and in the region of SiC source, it is possible to place the SiC source in a crucible having a hole in the bottom, by placing coaxially with the hole in the bottom of the crucible, a cylindrical graphite sleeve whose internal diameter is at least equal to the diameter of the hole in the bottom of the crucible, with the formation of area to place the SIC source between the inner surface of the crucible and the outer surface of the sleeve or by placing a plate of porous graphite fixed on the inner surface of the crucible walls above the bottom of the crucible to form an area for placing SiC source, bounded by the inner surface of the crucible and the upper surface of the plate. In the process of growth, mixture of inert gas with hydrogen is supplied, the content of which is from 2 vol.% to 20 vol.% , directly into the area of the SIC source location in the crucible through the formed channel for passage of gases.EFFECT: technical result of the invention is to reduce cost of the method, increase its productivity and improve quality of grown monocrystalline ingots SiC.3 cl, 2 dwg, 6 ex

Description

The invention relates to microelectronics and relates to a technology for producing single-crystal SiC, a widely used material used for the manufacture of integrated circuits.

When obtaining single-crystal SiC by sublimation on the lid of a graphite growth crucible, the plate of the SiC seed crystal is structurally fixed, a source of silicon carbide powder is placed in the crucible, the lid and growth crucible are combined with each other and sealed, and then the graphite crucible with the lid is placed in a growth chamber isolated from the atmosphere, with a carbon screen installed inside. Depending on the type of heating, the heating elements are placed either directly in the growth chamber, between the walls of the crucible and the heat shield (heating by means of a resistive graphite heater), or outside the growth chamber, coaxially to the crucible and the cylindrical growth chamber (heating by means of an RF inductor). Next, the growth chamber is evacuated using a vacuum system, filled with an inert gas using a gas inlet system, heated with a heating element that provides a temperature sufficient to sublimate the source - silicon carbide powder and the formation of silicon-containing volatile compounds. During heating, a temperature sufficient for sublimation is created in the growth chamber using a heating element and a heat shield, the growth chamber is pumped to a certain inert gas pressure, at which the process of transferring silicon-containing volatile compounds from the source to the SiC seed crystal wafer and growth of the single-crystal SiC ingot are activated .

When a growth chamber is heated with a crucible placed in it with an SiC source and a SiC seed crystal plate using a heating element, taking into account the heat-insulating ability of the heat shield, a thermal regime is established inside the growth chamber, characterized by a certain temperature distribution along the axis of the growth chamber. Despite the difference in heating elements and heat shields, all temperature distributions share common characteristics.

In the upper part of the growth chamber, the temperature when changing the coordinate along the axis of the growth chamber varies from about 20 ° C to about 2000 ° C. This zone of the growth chamber is characterized by high temperature gradients - the upper gradient zone.

In the lower part of the growth chamber, the temperature sharply decreases from about 2000 ° C to 20 ° C. This zone of the growth chamber is also characterized by high temperature gradients, which can be considered linear with a fairly good approximation - the lower gradient zone.

Between the upper and lower gradient zones is the middle zone - the zone of maximum heating, where the temperatures are maximum (T = 2000-2300 ° C). The temperatures achieved in this zone are sufficient for the sublimation process of growth of a single-crystal SiC ingot; when the coordinate along the axis of the growth chamber changes, the temperature changes relatively weakly.

The single crystal SiC ingot is grown in an inert gas atmosphere, usually in argon, as in the most accessible of pure inert gases. During evaporation with decomposition of the SiC source in an inert atmosphere, the SiC source is carbonized (excess carbon in the form of powder appears in the source), and the gas phase (silicon-containing volatile compounds) is enriched with excess silicon.

Silicon-containing volatile compounds formed in the inner space of the crucible during the growth of a single-crystalline SiC ingot seep through the gaps between the mating parts of the crucible and, to a lesser extent, through the pores in the crucible and the lid of the crucible, into the space of the growth chamber, and interact with thermal a screen (and also with a heating element - when placed inside the growth chamber), which forms the thermal distribution inside the growth crucible, which leads to the degradation of the properties of this screen (and also, accordingly , heating element) and the change in thermal conditions for the growth of a single-crystal SiC ingot from process to process. Such a change in thermal conditions will inevitably lead to a decrease in the yield of high-quality single-crystal SiC ingots and additional investment associated with the short life of the heat shields (and heating elements) and the need to replace them.

In addition, elemental powdery carbon resulting from the carburization of a SiC source can fall on the surface of a wafer of a SiC seed single crystal, causing degradation of the growing ingot and leading to a decrease in the yield of high-quality single-crystal SiC ingots.

Known methods for producing single-crystal SiC, allowing partially to get rid of these disadvantages.

So, in the method (RU 2621767, C30B 23/00, C30B 23/06, C30B 29/36, C23C 14/24, 2016), the crucible is installed in the growth chamber in the maximum heating zone so that part of its side walls is located in the upper the growth chamber, while the end of the side wall of the crucible is placed at a temperature of from 1000 to 1500 ° C. This technical solution allows to ensure the continuity of the walls of the crucible in the zone of maximum heating and prevents the exit of silicon-containing volatile compounds from the crucible into the surrounding space in the zone of maximum heating, increasing service life screen and heater, which leads to an increase in the yield of high-quality single-crystal ingots SiC and lower costs for carrying out the method.

A known method of producing single-crystal SiC, implemented using an apparatus for growing single-crystal SiC, in which between the side surfaces of the crucible and the heat shield that is placed around the outer surface of the crucible, create a gap of 5-40 mm (JP 2011219295, C30B 23/06, C30B 29 / 36, 2010). This technical solution allows to reduce the degradation of the properties of the heat shield, but does not affect the total flow of silicon-containing volatile compounds from the inner space of the crucible.

A number of methods for producing single-crystal SiC are known, which are realized using an apparatus for growing single-crystal SiC, in which the tightness of the conjugation of graphite parts of a growth crucible (crucible lid and the crucible itself) is improved. For this, the mating graphite parts are fixed relative to each other by means of a threaded connection located in a certain position relative to the source material (JP 2008074665, C30B 29/36, C30B 29/10, 2008).

There are also known methods and apparatus for growing high-quality single-crystal SiC ingots that use a graphite growth crucible with a threaded connection (JP 2006069851, C30B 29/36, C30B 29/10, 2006; EP 2365110, C30B 23/00, C30B 29/36, 2011; JP 2010202485 (A), C30B 23/06, C30B 29/36, H01L 21/203, 2010); to seal the mating parts of the crucible, high-temperature gaskets made of thermally expanded graphite are used (RU 2425914, С30В 23/00, С30В 23/02, С30В 29/10, 2011); the crucible and its lid are made of grades of graphite with a different coefficient of thermal expansion (JP 2005239464, C30B 29/36, H01L 21/203, C30B29 / 10, H01L 21/02, 2005). Such crucible designs reduce the degradation of heat-insulating screens located around the crucible, although they do not completely eliminate the interaction of heat-insulating screens with silicon-containing volatile compounds.

Completely exclude the flow of silicon-containing volatile compounds from the space inside the crucible into the space of the growth chamber allows the execution of the crucible and its lid from niobium or tantalum (US 2002059901, C30B 23/00, C30B 23/06, C30B 35/00, 1997) and a method for growing SiC single crystals using such a crucible (US 2002083891, C30B 23/00, C30B 23/06, C30B 35/00, 1997). Such a crucible absolutely does not pass silicon-containing volatile compounds through its walls, but it causes technological difficulties, since it is difficult to change the pressure inside the crucible by pumping the growth chamber.

Known methods in which changed the composition of the atmosphere in which the ingot is grown.

To obtain better single-crystal SiC ingots, growth is carried out in a growth atmosphere containing helium (partial pressure of at least 40 vol.%), As well as one of the inert gases from the group of neon, argon, krypton, xenon and radon (CN 102575383, С30В 23 / 00, C30B 29/36, 2012). For the same purpose, single-crystal ingots were grown in an atmosphere consisting of a non-corrosive gas (one of hydrocarbons) and an inert gas (argon, helium, and nitrogen) (JP 2009249207 (A), С30В 29/36).

Hydrogen is widely used to grow single-crystal SiC ingots, as a well-known cheap reducing agent and etchant. Thus, hydrogen is used as an element of the growth atmosphere to clean the surface of a wafer of a seed single crystal before initiating the growth process of a single-crystal ingot SiC (JP 2010100488 (A), C30B 29/36, 2010; JP 2008260665 (A), C30B 29/36, 2008), for annealing of single-crystal SiC ingots mixed with an inert gas (US 2009114924 (A1), С30В 25/00, С30В 29/36, 2009; JP 2006290705 (A), С30В 29/36, 2012), including in-situ annealing (EP 2653591, C30B 23/06, C30B 29/36, C30B 33/02, 2010), to reduce the nitrogen concentration in single-crystal SiC ingots and to obtain semi-insulating single-crystal SiC ingots (TW 200510264 (A), C30B 23 / 00, С30В 29/36, 2005), as well as single-crystal ingots with a controlled nitrogen content (TW 200510583 (A), С30В 23/00, 2005), for etching the surface of a wafer of a SiC seed single crystal (JP 2012051760, С30В 29/36, 2012 )

All of the above methods, changing the growth atmosphere of single-crystal ingots SiC, solved the problem of improving the quality of single-crystal ingots, however, with a possible increase in quality, the graphite reinforcement of the growth chamber, heat shield and graphite heater (with resistive heating) were destroyed due to their interaction as with silicon-containing volatile reagents, and with hydrogen. The rapid destruction of the heat shield and heater contributes to an uncontrolled change in the heat distribution in the growth chamber and to a deterioration in the quality of growing single-crystal SiC ingots. The negative result is also: high costs for expensive graphite parts, low yield of single-crystal SiC ingots, additional time required to replace graphite parts and clean the chamber of the growth chamber from the products of the interaction of graphite parts with the growth atmosphere, which leads to a decrease in the percentage of yield of single-crystal ingots and to increase the total amount of production costs per unit of useful products.

Closest to the claimed is a method of producing a single crystal ingot SiC (JP H08208380, C30B 23/00, C30B 29/36, H01L 33/34, 1996) by the method of freeze-drying recrystallization, which includes the step of growing a single crystal ingot of silicon carbide in a growth atmosphere containing from 1 ppm up to 90 rpm % hydrogen in an inert gas such as argon. Hydrogen atoms adsorbed on the surface of a plate of a seed single crystal SiC and on the surface of a growing single-crystal ingot SiC interact with carbon particles on this surface and give the ratio of silicon and carbon on the surface of a plate of a seed single crystal and, respectively, on the surface of a growing single-crystal ingot SiC to the stoichiometric required to create the perfect stoichiometric silicon carbide single crystal SiC. Argon atoms control the diffusion rate of molecules and, as a result, the growth rate of the SiC ingot.

Single crystal SiC ingot growth was performed as follows. The plate of the seed single crystal was fixed on the inner surface of the lid of a graphite growth crucible, a source of silicon carbide powder was poured into the crucible, after which the crucible was closed by a lid and placed inside the growth chamber on a graphite rod. Around the growth crucible was placed a heat shield of graphite felt. The walls of the growth chamber were a double quartz tube; heating was carried out using an rf heater.

A mixture of hydrogen and argon began to enter directly into the growth chamber, through a gas inlet mounted in the top cover of the growth chamber, when the temperature reached 2000 ° C. The temperature of the source was raised to 2400 ° C, after which it was pumped out to 10 Torr and the process of growing a single-crystal ingot SiC was carried out. The hydrogen concentration in the mixture with argon was set in the range from 1 ppm to 90 vol. % At a lower concentration, the effect of carbon etching on the seed single crystal wafer was not observed; at a higher hydrogen concentration, they could not control the diffusion of volatile silicon-containing particles with argon gas, i.e., it was not possible to control the growth rate of a single-crystal SiC ingot.

The disadvantage of this method is that the mixture of hydrogen and argon is fed directly to the growth chamber, and not to the growth crucible, where the hydrogen atoms adsorbed on the surface of the plate of a seed single crystal SiC and on the surface of a growing single crystal ingot SiC interact with carbon particles on this surface, improving the quality of the growing single-crystal ingot SiC. In order to get into a growth crucible, hydrogen and argon molecules must diffuse through the mass of the material of the heat shield made of graphite felt and through the walls of the growth crucible from dense graphite. As is known, hydrogen at temperatures above 1500 ° C actively reacts with carbon to form volatile hydrocarbons (methane, acetylene). Thus, the addition of hydrogen to the space of the growth chamber during the growth of single-crystal silicon carbide ingots not only allows etching of the residual carbon on the surface of the growing single-crystal SiC ingot, but also leads to the etching of graphite reinforcement, heat shield and, when using resistive heating, a heater. The interaction of hydrogen with graphite fittings, a heat shield and a heater leads to their premature wear, which in turn leads to a rise in the cost of the growing process (replacement of fittings).

In addition, when hydrogen diffuses through bulk graphite parts made of graphites of various grades and heated to different temperatures, it is practically impossible to determine how much hydrogen reacts with graphite reinforcement and how much hydrogen enters the growth crucible. Thus, the amount of hydrogen in the growth atmosphere under the conditions presented in the prototype application will always be excessive, and the conditions in the growth crucible will always be irreproducible, which leads to instability of the growth rate of single-crystal SiC ingots. Because of this, the productivity of the method decreases and the quality of single-crystal SiC ingots deteriorates.

The objective of the invention is to provide a method for producing single-crystal SiC, providing a technical result, which consists in reducing the cost of carrying out the method, increasing its productivity and improving the quality of grown single-crystal SiC ingots.

The essence of the proposed method lies in the fact that upon receipt of a single-crystal SiC ingot by sublimation of a SiC source placed in a growth crucible, followed by condensation of vapors on a plate of a SiC seed single crystal, in a growth atmosphere consisting of a mixture of inert gas and hydrogen in a growth chamber with an aperture in the bottom, a crucible having a hole in the bottom is placed by mounting it on a holder with a base having a hole and fixed to a rod with a longitudinal hole that passes through the hole in the bottom of the chamber , so that the holes in the bottom of the crucible, in the base of the holder and in the rod form a single channel for the passage of a gas mixture of inert gas and hydrogen in the crucible, in the area of the source, provide the ability to place the SiC source in the crucible with the hole in the bottom, and during the growth process, a mixture of inert gas with hydrogen is supplied, the content of which is from 2 to 20 vol. % directly to the zone of location of the SiC source in the crucible through a single channel formed by holes in the crucible, the base of the holder and the rod.

The crucible can be made with side walls whose height exceeds the longitudinal size of the working volume of the crucible, and part of the side walls located above the crucible cover is located in the upper zone of the growth chamber, so that the end face of the side wall of the crucible is placed at a temperature of from 1000 to 1500 ° C.

The ability to place a SiC source in a crucible having a hole in the bottom can be achieved by placing a cylindrical graphite sleeve, the inner diameter of which is at least equal to the diameter of the hole in the bottom of the crucible, coaxially with the hole on the bottom of the crucible, with the formation of a region for placing the SiC source between the inner surface crucible and the outer surface of the sleeve.

The ability to place the SiC source in a crucible having an opening in the bottom can be achieved by placing it fixed on the inside

the surface of the walls of the crucible of the plate of porous graphite above the bottom of the crucible with the formation of the area for the source of SiC, limited by the inner surface of the crucible and the upper surface of the plate.

Inert gas is selected from a series of helium, neon, argon, krypton, xenon, radon.

When a mixture of inert gas with hydrogen is introduced through a single channel directly into the crucible, in the zone where the source is located on the path of the gas flow into the growth crucible, there are no volumetric graphite parts (valves, heat shield, heater) that actively interact with hydrogen and reduce the hydrogen concentration. Therefore, the introduction of a mixture of inert gas and hydrogen through a single channel directly into the growth crucible leads, firstly, to minimizing the amount of hydrogen used in the process of growing a single-crystal SiC ingot, and, consequently, to increasing the service life of graphite reinforcement, screen and heater, secondly secondly, to a high reproducibility of the process of growing ingots of single-crystal SiC and an increase in the yield of suitable ingots, since hydrogen is delivered locally to the crucible, primarily interacting with carbon in needle, including a carbon source in obuglerozhennom and carbon on the surface of the seed and the growing ingot.

An important issue is the amount of hydrogen required to implement the method. Hydrogen interacting with carbon in the growth crucible in the source zone at the temperatures of growing a single-crystal SiC ingot leads to an increase in carbon transport and the achievement of a stoichiometric Si / C ratio in the growth atmosphere. Thus, hydrogen prevents carbonization of the source and the entry of elemental powdered carbon onto the surface of the wafer of a seed single crystal or a growing SiC ingot, improving the quality of the SiC crystal.

At the same time, the active interaction of hydrogen with carbon and silicon carbide on the surface of a growing single-crystal ingot SiC leads to a decrease in such an important technological parameter of the growing process as the observed growth rate of the ingot, since the observed growth rate is the sum of two processes on the surface of the growing ingot - deposition of silicon carbide from the gas phase and its etching with hydrogen, and it is obvious that the etching rate is proportional to the amount of free hydrogen.

The lower limit of the amount of hydrogen that must be added to the inert gas is determined by the observed improvement in the quality of the growing ingots, which can be fixed. According to our experimental estimates, this value is 1-2 vol. % of inert gas.

The upper limit of the amount of hydrogen that can be added to an inert gas is determined by the combined influence of two factors: a decrease in the observed growth rate of a single-crystal SiC ingot and a decrease in the service life of graphite fittings, a heat shield, and a heater. According to our experimental estimates, this value is 10–20 vol. % hydrogen. At 20 vol. % hydrogen, the growth rate of the SiC ingot decreases by 4–5 times compared with the growth rate of a single-crystal ingot in a growth atmosphere without the addition of hydrogen; damage to graphite reinforcement is insignificant.

To ensure the supply of a mixture of inert gas and hydrogen directly to the growth crucible, in the source placement zone, structural changes were made in the SiC source placement zone, preventing loss of the SiC source through the hole in the bottom of the growth crucible (in other words, the precipitation of SiC powder through the hole in the bottom of the growth crucible).

Losses of the source material can be prevented by using a porous thin-walled graphite sleeve located vertically in the growth crucible and fixed between the crucible cover and its bottom, coaxially with the hole in the bottom of the growth crucible. The inner diameter of the sleeve must exceed the diameter of the hole in the bottom of the growth crucible. The thickness of the walls of the sleeve is 1-2 mm, the walls must be permeable to the components of the vapor phase, for the diffusion of the latter from the source into the channel for the passage of the gas mixture.

Another constructive solution to prevent loss of material from the source is to place a thin porous graphite plate on an additional step made on the inner surface of the walls of the growth crucible. The mixture of gases forming the growth atmosphere enters the space formed by the crucible walls, the bottom of the crucible and a thin porous graphite plate, and diffuses through the porous plate, falling into the source space bounded by the inner surface of the crucible walls and the upper surface of the porous plate. The plate must be strong enough to support the weight of the source (2-4 kg of silicon carbide powder) and permeable to vapor phase components. In this case, an uninterrupted supply of a mixture of gases forming the atmosphere of growth into the zone of the source of the growth crucible is ensured, as well as the absence of source losses.

When a single-crystal SiC ingot is grown in a growth atmosphere containing an exclusively inert gas, the volatile compounds formed in the inner space of the crucible and seeping through the gaps between the mating parts into the space of the growth chamber are strongly enriched in gaseous silicon, which interacts in cooler regions of the growth chamber with graphite fittings, a heat shield and a heater, resulting in the deposition of polycrystalline carbide on their surfaces at a temperature of 1000-1500 ° C silicon. The addition of hydrogen, as mentioned above, leads to an increase in carbon transport, due to the formation of a number of hydrocarbons, especially acetylene and methane, and to a more stoichiometric gas phase inside the growth crucible (i.e., in the gas phase Si / C≈1). Part of the volatile compounds still seeps into the space of the growth chamber, but, due to the better stoichiometry of the gas phase (higher carbon content), the volatile silicon and carbon compounds interact with each other, the graphite fittings, the heat shield, and the heater are better preserved and have a longer service life. The time-stable properties of the heat shield and heater can increase the productivity of the method and prevent changes in the quality characteristics of the grown single-crystal SiC ingots from ingot to ingot.

To further increase the service life of graphite reinforcement, heat shield and heater, the growth crucible can be structurally made with side walls whose height exceeds the longitudinal size of the working volume of the growth crucible and part of which is located in the upper zone of the growth chamber, so that the end of the side wall of the growth the crucible is placed at a temperature of from 1000 to 1500 ° C. This configuration of the growth crucible leads to the fact that a small amount of volatile silicon and carbon compounds penetrating through the gaps between yshkoy and the crucible and diffusing upward along the inner wall surface of the growth crucible at a temperature below 1500 ° C, in accordance with the phase diagram, are in a solid state, condenses on the inner wall surface of the growth crucible.

The method is illustrated by drawings.

FIG. 1 is a diagram of a sublimation installation for implementing the proposed method (a cylindrical porous sleeve is installed in the growth crucible);

FIG. 2 is a diagram of a sublimation apparatus for implementing the proposed method (a thin porous plate is placed in the growth crucible).

As a technical means for implementing the proposed method for producing single-crystal SiC, a freeze-drying apparatus for growing single-crystal SiC is used (Fig. 1), which contains a cylindrical vacuum growth chamber 1, to which a vacuum system and a gas inlet system are connected.

The gas inlet system consists of two gas lines - A and B. Gas line A serves to inert gas inlet into the growth chamber, into the space between the walls of the chamber 1 and the heat shield 2 made of carbon materials. Gas line B is intended for the inlet of a mixture of inert gas and hydrogen directly into the growth crucible 5, in the area of the source of SiC.

Highway B serves to fill the gas mixture directly into the growth crucible 5, to obtain a technical result according to the proposed method. Line A serves to inert gas inlet into the growth chamber 1 in the process of entering the regime before growing the ingot, when the growth chamber 1 is filled with inert gas with a high flow rate and it is undesirable to pass all inert gas through the source zone, in order to avoid the appearance of suspended carbon or silicon carbide particles in the space of the growth crucible and surface contamination of the seed plate of the single crystal.

Through the hole in the bottom of the growth chamber 1, through the vacuum-tight connection, the rod of the holder 3 is inserted into the growth chamber 1, at the upper end of which the base of the crucible holder 4 is placed. The crucible 5 is located on the base of the crucible holder 4. The rod of the crucible holder 3 is constructed in the form of a hollow rod with axial longitudinal hole. Holes are also made in the bottom of the crucible 5 and in the base of the crucible holder 4. When assembling the crucible holder 5 by connecting the rod of the crucible holder 3 and the base of the crucible holder 4 and then placing it on the assembled crucible holder 5, the holes in the bottom of the crucible 5, in the base of the crucible holder 4 and in the rod of the crucible holder 3 coincide, forming a single channel for gas passage mixture 6, which is connected to the gas line B. If necessary, the joints of the rod, the base of the holder and the crucible are sealed with high-temperature gaskets of high-purity thermally expanded graphite. A mixture of gases (inert gas - usually argon - and hydrogen) from line B enters channel 6 for the passage of the gas mixture and then directly into the growth crucible 5, in the zone where the SiC 12 source is located.

When carrying out the method, a growth crucible 5 with a crucible cover 7, a bottom of the crucible 8 and the side walls of the crucible 9 is placed on the base of the crucible holder 4. The cap 7 is mounted on a ledge made on the inner surface of the side walls of the crucible 9.

Inside the cavity formed by the heat shield 2, a resistive graphite heater 10 is arranged coaxially with it, heating the growth crucible 5 (in the case of RF heating, the heater is located on the outside of the side walls of the growth chamber).

In a sublimation unit (Fig. 1) in a growth crucible 5, in the space between the bottom of the crucible 8 and the lid of the crucible 7, a cylindrical sleeve of porous graphite 11 is installed coaxially with the growth crucible 5, the inner diameter of which exceeds the diameter of the hole in the bottom of the crucible 8. In the space between the inner by the surfaces of the walls of the crucible 9 and the outer surface of the cylindrical sleeve 11, a source 12 of SiC powder is loaded. The lid of the crucible 7 simultaneously serves as the holder of the plate of the seed single crystal 13, which is fixed on the lower surface of the lid of the crucible 7.

In a sublimation installation (Fig. 2), a thin plate of porous graphite 14 is installed in the growth crucible 5, on an additional step made on the inner surface of the walls of the crucible 9. The source 12 is loaded into the space bounded by the upper surface of the thin plate 14 and the inner surface of the walls of the crucible 9. The lid of the crucible 7 simultaneously serves as the holder of the plate of the seed single crystal 13, which is fixed on the lower surface of the lid of the crucible 7.

The method is as follows (Fig. 1, Fig. 2).

Previously, through the hole in the bottom of the growth chamber 1, the rod of the crucible holder 3 is inserted into the growth chamber and fixed by means of a vacuum tight connection, the base of the crucible holder 4 is fixed at its upper end. Also, a resistive heater 10 and a heat shield 2 are placed in the growth chamber 1.

In a growth crucible 5 having an opening in the bottom:

- either place a thin-walled graphite sleeve 11 (Fig. 1), fixed between the bottom of the crucible 8 and the cover of the crucible 7 coaxially with the hole in the bottom of the crucible, and the inner diameter of the graphite sleeve is larger than the diameter of the hole in the bottom of the crucible. Thus, the space inside the sleeve is connected to the channel for the passage of the gas mixture 6. In the space bounded by the side walls of the crucible 9, the bottom of the crucible 8 and the outer walls of the thin-walled graphite sleeve 11, a source 12 is placed - silicon carbide powder;

either on the inner surface of the side walls of the growth crucible 5, also having an opening in the bottom 8, a plate of porous graphite 14 is fixed (Fig. 2), and a source 12 is placed in the space above the plate 14.

A plate of the seed single crystal 13 is fixed on the lid of the crucible 7, after which the lid of the crucible 7 is installed in the crucible 5, and the crucible 5 is placed inside the growth chamber 1, on the base of the holder 4.

The growth chamber 1 is isolated from the atmosphere and vacuum using a vacuum system, filled with an inert gas using a gas injection system on line A and heated using a heating element 10, providing a temperature sufficient to sublimate the source 12 and the formation of silicon-containing volatile compounds. When the required temperature is reached, the gas mixture (for example, argon and hydrogen) is supplied from the gas line B to the channel for passing the gas mixture 6 with a certain volumetric flow rate and percentage of components, which is maintained until the end of the growth process of the single-crystal SiC ingot.

The gas mixture (inert gas and hydrogen) supplied to the channel for passage of the gas mixture 6, with minimal losses, falls directly into the space inside the growth crucible 5, in the zone of the SiC source.

After the exposure necessary for thermal stabilization of the growth crucible 5, the growth chamber 1 is pumped to a gas mixture pressure (for example, argon and hydrogen), at which the process of transferring silicon-containing volatile compounds from source 12 to the seed crystal single crystal plate 13 and the growth of a single-crystal SiC ingot is activated.

The ingot is grown, maintaining the achieved pressure in the growth chamber 1 (dynamic equilibrium between the supply of the gas mixture to the growth chamber 1 through the gas inlet system and the regulated pumping of the gas mixture from the growth chamber 1 through the vacuum system) and the temperature in the crucible is sufficient to sublimate the source.

When using the first constructive solution for locating the source (Fig. 1), silicon-containing volatile compounds formed in the source 12 diffuse through the thin walls of the thin-walled graphite sleeve 11 and fall into the region bounded by the inner surface of the thin-walled graphite sleeve 11, where they are mixed with the flow of gases going through channel 6 for passage of the gas mixture from line B inside the crucible 5, to the plate of the seed single crystal 13. In turn, the gas mixture (inert gas and hydrogen) supplied to the plate of a single crystal 13 through the channel 6 for the passage of the gas mixture, also diffuses through the wall of the sleeve 11 into the region of the source 12, where it is mixed with volatile silicon-containing compounds.

When using the second design solution for placing the source (Fig. 2), the gas mixture enters the space bounded by the bottom of the crucible 8, the walls of the crucible 9 and the plate of porous graphite 14, diffuses through the porous plate 14, mixes with silicon-containing volatile compounds at the source 12, and reaches single crystal wafer 13.

After the process of growing a single-crystal SiC ingot is completed, growth chamber 1 is cooled to room temperature and depressurized. The quality of the grown ingot is evaluated visually, as well as after sawing the ingot into plates, grinding and polishing, by selective wet etching in a KOH melt, for 5 minutes at a temperature of 550 ° C and optical microscopy.

The growth rate of a single-crystal ingot is determined by direct measurement, as well as by the gravimetric method, at a known density and diameter of the ingot.

The condition of the graphite reinforcement, the main screen 2 and the heater 10 is evaluated visually, by traces of corrosion on the surface of graphite, as well as by the distribution of the precipitate of polycrystalline silicon carbide on graphite surfaces.

The rationale for the design parameters of the method is given in the examples.

Various substances can be used to create elements of graphite fittings, a heater, and a heat shield. In particular, these can be various grades of graphites or refractory metals that are stable in the environment of silicon-containing volatile compounds at the growth temperature of a single-crystal ingot SiC. The most preferred is the use of the crucible, the base of the holder and the rod of a sufficiently dense, but relatively inexpensive structural graphite (A2, MG, etc.). The gas permeability of the walls in this case is extremely small.

High-purity gases - argon (grade 5N5) and hydrogen (6N) are usually used to create a growth atmosphere. Argon is the most affordable and cheapest of inert gases, but any of the family of inert gases — helium, neon, argon, krypton, xenon, radon — can be used to create an inert growth atmosphere.

Porous graphite sleeve 11 and plate 13 can be made of special grades of highly porous graphite (VK-20, PG-50) or the cheapest electrode graphite HE.

The method is implemented in a system with resistive heating, but can also be applied in a system with rf heating, in which the rf heater, which heats the growth crucible 5, is located outside the growth chamber 1. For a system with resistive heating, the implementation of the method will increase the service life not only graphite fittings, heat shield 2, but also resistive heating elements 10.

Example 1. Used growth crucible 5 of graphite grade GE with pyro-sealing, with an inner wall diameter of 170 mm and an overall height of 385 mm.

In the bottom of the crucible 5, a hole with a diameter of 15 mm is structurally made. A sleeve 11 of porous graphite with an inner diameter of 55 mm and a wall thickness of 1 mm was placed in crucible 5. 1.6 kg of high-purity SiC powder manufactured by Saint Gobain (Norway), with a grain size of 100 μm, was used as a source 12 in a space bounded by the outer walls of porous graphite bushing 11 and the inner surface of the walls of the crucible 9. A seed crystal plate 13 with a diameter of 13 was used 2 inches of polytype 4H with a nominal orientation (0001) with a deviation of 4 ° in the [11-20] direction with an average pore density of 10-30 cm ^-2 , which was fixed on the lid of the crucible 7. The lid of the crucible 7 was placed in a growth crucible 5, on a ledge made on the internal the surface of the walls of the crucible 9, after which the crucible 5 was placed in the growth chamber 1, on the base of the holder 4, in which structurally

made a hole with a diameter of 12 mm. In the body of the rod 3 with a diameter of 30 mm, a longitudinal hole of 12 mm is also made. The holes in the bottom of the crucible 5, the base of the holder 4 and the rod of the holder 3 when installing the crucible 5 form a channel for the passage of the gas mixture 6, connected to the highway B.

The growth chamber 1 was pumped to a pressure of 10 ^-3 mm RT. Art. The growth crucible 5 was heated to 1200 ° C using a resistive heater 10 and held for 3 hours to remove residual contaminants.

After that, growth chamber 1 was filled with high-purity argon along line A to a pressure of 500 mm Hg. Art. (flow rate 5 l / hour). After reaching the specified pressure, the following flows along the gas lines were kept fixed:

Highway A: gas - argon, 0.5 l / h;

Highway B: gas - argon + hydrogen (10 vol.%), 1 l / h.

The achieved pressure in the growth chamber 1 was maintained at 500 mm RT. Art., using an adjustable pumping along the vacuum line.

The growth crucible 5 was heated to a source temperature of 12 2150 ° C. The temperature of the plate of the seed single crystal 13 was 2120 ° C.

After thermal stabilization for 1 hour, the growth chamber 1 was pumped out (with constantly operating gas flows along lines A and B) to a pressure of 2 mm Hg. Art. At this pressure, a single-crystal SiC ingot grew on the plate of the seed single crystal 13 for 20 hours.

At the end of growing a single-crystal ingot SiC, growth chamber 1 was cooled to room temperature and depressurized. A single-crystal ingot of 4T polytype silicon carbide was extracted from a growth crucible 5. The thickness of the ingot was 8 mm, i.e., the growth rate of the ingot was 0.4 mm / h.

The density of micropores did not exceed 5 cm ^-2 , which indicates the high quality of the ingot.

There were no traces of corrosion on the surfaces of the heater 10 and the heat shield 2, on graphite reinforcement inside the crucible 5, in the space above the crucible cover 7, mild deposition of polycrystalline silicon carbide was observed.

Example 2. The same basic process parameters were used as in example 1. After reaching a pressure of 500 mm RT. Art. The following flows along the gas mains were kept fixed:

Highway A: gas - argon, 0.5 l / h;

Highway B: gas - argon, 1 l / h.

After thermal stabilization, the growth chamber 1 was pumped out for 1 hour (at constant operating flows along lines A and B) to a pressure of 6 mm Hg. Art., growth was carried out for 10 hours.

The thickness of the single crystal ingot was 6 mm, that is, the growth rate of the ingot is 0.6 mm / h. The density of micropores in the SiC ingot was 40-50 cm ^-2 , which indicates insufficient quality due to the lack of hydrogen. Abundant precipitation of polycrystalline SiC is observed in the growth crucible 5, in the space above the crucible cover 7, as well as on separate parts of the heater 10, near cooled current leads.

Example 3. The same basic process parameters were used as in example 1. After reaching a pressure of 500 mm RT. Art. The following flows along the gas mains were kept fixed:

Highway A: gas - argon, 0.5 l / h;

Highway B: gas - argon + hydrogen (30 vol.%), 1 l / h.

After thermal stabilization for 1 hour, the growth chamber 1 was pumped out (with constantly operating flows along the highways A and B) to a pressure of 1 mm Hg. Art., growth was carried out for 20 hours.

The thickness of the ingot was 3 mm, that is, the growth rate of the ingot is 0.15 mm / h (low growth rate due to the large amount of hydrogen). The density of micropores in the SiC ingot was 0–10 cm ^–2 (a rather high quality single crystal SiC ingot). The deposition of polycrystalline SiC in the growth crucible 5, in the space above the lid of the crucible 7, is not observed. Carbonization of the current-carrying parts in the cold zone of the growth chamber is observed, apparently due to carbon transfer through hydrocarbon transport (reduced service life of graphite fittings, heat shield and heater due to excess hydrogen).

Example 4. Used a crucible 5 of graphite grade GE with pyro-sealing, with an inner wall diameter of 170 mm and an overall height of 385 mm.

In the bottom of the crucible 5, a hole with a diameter of 15 mm is structurally made. In the crucible 5, on a ledge made on the inner surface of the walls of the crucible 9, a plate 14 of porous graphite 2.5 mm thick was placed. In a space bounded by the upper surface of the plate 14 and the inner surface of the walls of the crucible 9, 2.5 kg of high-purity SiC powder manufactured by Saint Gobain (Norway), with a grain size of 100 μm, was placed as a source 12.

We used a plate of a seed single crystal 13 with a diameter of 3 inches of a 4H polytype with a nominal orientation (0001) with a deviation of 4 ° in the [11–20] direction with an average pore density of 10–30 cm ^–2 . The lid of the crucible 7 simultaneously serves as the holder of the plate of the seed single crystal 13. The lid 7 was placed in the crucible 5, on another ledge made on the inner surface of the walls of the crucible 9, after which the crucible 5 was placed in the growth chamber 1, on the base of the holder 4, in which it is structurally made hole with a diameter of 12 mm. In the body of the rod 3 with a diameter of 30 mm, a longitudinal hole of 12 mm is also made. The holes in the bottom of the crucible 5, the base of the holder 4 and the stem of the holder 3 when installing the crucible 5 form a channel for the passage of the gas mixture connected to the line B.

The growth chamber 1 was pumped to a pressure of 10-3 mm RT. Art. The crucible 5 was heated to 1200 ° C using a resistive heater 10 and held for 3 hours to remove residual contaminants.

After that, growth chamber 1 was filled with high-purity argon along line A to a pressure of 500 mm Hg. Art. (flow rate 5 l / hour). After reaching the specified pressure, the following flows along the gas lines were kept fixed:

Highway A: gas - argon, 0.5 l / h

Highway B: gas - argon + hydrogen (10 vol.%), 1 l / h.

The achieved pressure in the growth chamber 1 was maintained at 500 mm RT. Art., using an adjustable pumping along the vacuum line.

Crucible 5 was heated to a source temperature of 12 2150 ° C. The temperature of the plate of the seed single crystal 13 was 2120 ° C.

After thermal stabilization, growth chamber 1 was pumped out for 1 hour (at constant operating flows along lines A and B) to a pressure of 1 mmHg. At this pressure, a single-crystal SiC ingot grew on a seed plate 13 for 20 hours.

At the end of growing a single-crystal ingot SiC, growth chamber 1 was cooled to room temperature and depressurized. A single-crystal ingot of silicon carbide polytype 4H was extracted from crucible 5. The thickness of the ingot was 9 mm, i.e., the growth rate of the ingot was 0.45 mm / h.

The micropore density did not exceed 5 cm ^-2 (high quality of the grown single-crystal SiC ingot).

There were no traces of corrosion on the surfaces of the heater 10 and the heat shield 2, on graphite reinforcement inside the crucible 5, in the space above the crucible cover 7, mild deposition of polycrystalline silicon carbide was observed.

Example 5. The same basic process parameters were used as in example 4. After reaching a pressure of 500 mm RT. Art. The following flows along the gas mains were kept fixed:

Highway A: gas - argon, 0.5 l / h,

Highway B: gas - argon + hydrogen (30%), 1 l / h.

After thermal stabilization, the growth chamber 1 was pumped out for 1 hour (with constantly operating flows along the highways A and B) to a pressure of 2 mm Hg. Art., growth was carried out for 20 hours.

The thickness of the ingot was 2 mm, that is, the growth rate of the ingot is 0.10 mm / hour (low growth rate due to excess hydrogen). The micropore density in the SiC ingot was 0-10 cm ^-2 (high quality single-crystal SiC ingot). The deposition of polycrystalline SiC in the growth crucible 5, in the space above the lid of the crucible 7, is not observed. Carbonization of the current-carrying parts in the cold zone of the growth chamber is observed, apparently due to carbon transfer through hydrocarbon transport (reduced service life of graphite fittings, heat shield and heater due to excess hydrogen). Example 6. The same basic process parameters were used as in example 4. After reaching a pressure of 500 mm RT. Art. The following flows along the gas mains were kept fixed:

Highway A: gas - argon, 0.5 l / h;

Highway B: gas - argon + hydrogen (1.5 vol.%), 1 l / h.

After thermal stabilization for 1 hour, the growth chamber 1 was pumped out (with constantly operating flows along the highways A and B) to a pressure of 4 mm Hg. Art., growth was carried out for 20 hours.

The thickness of the ingot was 10 mm, that is, the growth rate of the ingot is 0.50 mm / hour. The micropore density in the SiC ingot was 10–50 cm ^–2 (a decrease in the quality of the grown single-crystal SiC ingot). Intensive precipitation of polycrystalline SiC is observed in the growth crucible 5, in the space above the crucible cover 7.

As can be seen from the above examples, the use of the proposed method allows to obtain the claimed technical result.

The increase in hydrogen content above 20 vol. % in the total volume of the gas mixture feeding the growth crucible 5 reduces the growth rate to commercially unacceptable values (below 0.3 mm / h) and leads to excessive transport of carbon through the formation of hydrocarbons. Such transport leads to a decrease in the service life of graphite fittings, the main screen 2 and the heater 10, in the case of using resistive heating, that is, it leads to an increase in the cost of the method.

The decrease in hydrogen content below 2 vol. % leads to the disappearance of the positive effect associated with an improvement in the structural perfection of growing ingots. A more pronounced interaction of silicon-containing volatile compounds with graphite reinforcement is also observed.

With a hydrogen content of 2-20 vol. % there is an effect associated with an improvement in the structural perfection of growing single-crystal SiC ingots. At the same time, there was no negative effect associated with a reduction in the service life of graphite fittings, heat shield 2 and heater 10, in the case of resistive heating.

Thus, the claimed method allows to achieve a technical result, which consists in reducing the cost of carrying out the method, increasing its productivity and improving the quality of grown single-crystal SiC ingots.

Claims (3)

1. A method of producing single-crystal SiC, including sublimation of a source of SiC placed in a crucible onto a plate of a seed single crystal of SiC, where the stage of growth of a single crystal of SiC is carried out in an atmosphere of a gas mixture of inert gas and hydrogen, characterized in that a crucible having a hole in the bottom is placed in the growth chamber by installing it on the crucible holder having an axial through hole, so that the holes in the bottom of the crucible and in the holder form a channel for the passage of gases, and in the area of the SiC source provide the opportunity for substituting a SiC source in a crucible having an opening in the bottom by placing a cylindrical graphite sleeve, the inner diameter of which is at least equal to the diameter of the opening in the bottom of the crucible, coaxially with the opening in the bottom of the crucible, with the formation of a region for placing the SiC source between the inner surface of the crucible and the outer the surface of the sleeve or by placing a plate of porous graphite fixed on the inner surface of the walls of the crucible above the bottom of the crucible with the formation of the region for the source of SiC, bounded by the inner surface south of the crucible and the upper surface of the plate, while in the process of growth, a mixture of inert gas with hydrogen, the content of which is 2-20 vol.%, is supplied directly to the zone of the SiC source in the crucible through the formed channel for the passage of gases. 2. The method of producing single-crystal SiC according to claim 1, characterized in that the crucible is made with side walls whose height exceeds the longitudinal size of the working volume of the crucible, and part of the side walls located above the crucible cover is located in the upper zone of the growth chamber so that the end of the side wall of the crucible is placed at a temperature of from 1000 to 1500 ° C. 3. The method of producing single-crystal SiC according to claim 1, characterized in that the inert gas is selected from the series helium, neon, argon, krypton, xenon, radon.

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