KR20070072670A - Apparatus for growing single crystal and method for growing single crystal - Google Patents

Abstract

An apparatus for growing a single crystal is provided to prevent formation of polycrystal and grow a silicon carbide single crystal having a uniform content of impurities by independently controlling heating and supplying of a single crystalline material and impurities. A seed(30) and a single crystalline material are prepared in a single crystalline material crucible(10). An impurity crucible(40) in which impurities are prepared is connected to the single crystalline material crucible. First and second heating units are respectively installed outside the single crystalline material crucible and the impurity crucible. The first and second heating units are independently operated, separated from each other by a predetermined interval and including RF induction coils(90,100). Impurity gas is transferred form the impurity crucible to the single crystalline material crucible by an impurity gas supplying pipe(50).

Description

Apparatus for growing single crystal and method for growing single crystal

1 and 2 are schematic cross-sectional views showing a conventional single crystal growth apparatus.

3 is a photograph showing a case in which a polycrystal is formed on a conventional seed crystal.

4 is a schematic cross-sectional view showing a single crystal growth apparatus according to the present invention.

<Explanation of symbols for the main parts of the drawings>

10: single crystal raw crucible 20: crucible lid

30: seed crystal 40: impurity crucible

50 impurity gas supply pipe 60 carrier gas supply pipe

70: heat insulating material 80: double quartz tube

90, 100: high frequency induction coil

The present invention relates to a single crystal growth apparatus and a single crystal growth method, and more particularly, to a single crystal growth apparatus and a single crystal growth method for growing a silicon carbide single crystal by a sublimation recrystallization method.

Since the 1960s to date, silicon (Si), which has been used as a representative semiconductor device material, has revealed physical limitations, and various compound semiconductor materials have been studied as a new semiconductor device material to overcome this problem. Next-generation semiconductor device materials are expected to be promising broadband semiconductor materials such as SiC, GaN, AIN, and ZnO. In particular, silicon carbide (SiC) has excellent thermal stability at 1500 ° C or lower, excellent stability in an oxidizing atmosphere, and has a large thermal conductivity of about 4.6W / cm ° C. Or more useful than Group III-V compound semiconductors such as GaN. Although silicon carbide (SiC) has a smaller electron mobility than silicon, its bandgap is twice or three times that of silicon, and its operating limit temperature is 650 ° C. Thus, it has a much higher operating limit temperature than silicon having an operating limit temperature of 200 ° C or less. There is an advantage to having. It is also chemically and mechanically strong, making it a device that can be used in extreme environments.

Thus, silicon carbide (SiC) has attracted attention as an environmentally resistant semiconductor material from physical and chemical properties such as excellent heat resistance and mechanical strength, and strong against radiation. In addition, the demand for SiC single crystal wafers as substrate wafers, such as short wavelength optical devices and high frequency high breakdown voltage electronic devices, ranging from blue to ultraviolet light is increasing.

Conventionally, silicon carbide single crystals having a size capable of manufacturing semiconductor devices have been obtained by using the sublimation recrystallization method (Railey method) for the production of the silicon carbide single crystal. However, this method has a small area of the single crystal thus obtained, and it is difficult to control its dimensions and shapes with high accuracy. In addition, it is not easy to control the crystal polymorph and impurity carrier concentration of silicon carbide.

In addition, a method of growing a cubic silicon carbide single crystal by growing heteroepitaxial on a heterogeneous substrate such as silicon (Si) using a chemical vapor deposition method (CVD method). In this method, a large area single crystal is obtained, but it is not easy to grow a silicon carbide single crystal containing defects due to lattice mismatch with the substrate, and to obtain a high quality silicon carbide single crystal.

In order to solve this problem, an improved Rayleigh method of sublimation recrystallization using a wafer made of silicon carbide single crystals as seed crystals (seed) has been proposed. This method uses seed crystals to control the nucleation process of single crystals. In addition, by controlling the atmospheric pressure using an inert gas, the growth rate and the like of the single crystal can be controlled with good reproducibility.

In brief, silicon carbide crystals, which are used as raw materials, are stored in a crucible made of graphite, for example, and silicon single crystals having seed crystals are disposed thereon. By forming a temperature gradient, the raw material in the crucible is diffused to the seed crystal side and recrystallized to grow a single crystal. At this time, the resistivity of the grown single crystal can be controlled by partially replacing impurities. Representative substitution type impurities in silicon carbide single crystals include nitrogen (n-type), boron, and aluminum (p-type).

The single crystal growth in which such an impurity is added can be achieved by mixing an impurity element or a compound thereof in the silicon carbide crystal powder or adding an impurity gas in an inert gas atmosphere.

1 and 2 are schematic cross-sectional views of a growth apparatus illustrated to explain a single crystal growth process to which a conventional impurity is added.

Conventionally, in order to manufacture a single crystal added with impurities, a mixture of single crystal raw material (A) and impurities (B) is charged into the crucible 1 in a constant ratio using a general single crystal growth apparatus as shown in FIG. And then sublimed to grow single crystals. Referring to FIG. 1, the single crystal growth apparatus includes a crucible 1 having a seed crystal 3 attached to an upper portion thereof, that is, a crucible lid 2 and a single crystal raw material A loaded therein, and the crucible 1. And a high frequency induction coil 6 for heating the crucible 1 outside thereof.

However, in this case, since most of the impurities (B) having a relatively low sublimation temperature are first sublimed at a lower temperature than the single crystal raw material (A), excessive sublimation of impurities occurs at the beginning of growth, and the impurities rapidly increase as the growth proceeds. A decrease occurs. Thus, there is a problem that the substitution of impurities in the grown single crystal is not uniform. Furthermore, the sublimed impurities prior to the single crystal raw material can apply the seed crystal 3 to form the polycrystal C as shown in FIG. 3.

In order to solve this problem, the single crystal raw material A and the impurity gas (sublimation) are injected by injecting the impurity B into the reaction gas using a single crystal growth apparatus as shown in FIG. 2 without mixing the single crystal raw material and impurities. A method of growing single crystals by reacting B) has been proposed. Referring to FIG. 2, the single crystal growing apparatus is substantially the same as the single crystal growing apparatus of FIG. 1 described above, but the crucible is passed through the lower surface of the crucible 1 into which the single crystal raw material A is charged from the bottom of the crucible 1. It further includes an impurity gas supply pipe 7 extending into the interior of (1). Impurity gas (B) is supplied through the impurity gas supply pipe (7), which is transferred into the crucible (1) and reacts with the single crystal raw material sublimed in the crucible (1), thereby forming on the seed crystal (3). Single crystals to which impurities are added are grown. Thus, it is possible to grow a single crystal to which impurities are added uniformly, and to prevent the formation of polycrystals. However, this method has a disadvantage in that it is not suitable for producing a p-type impurity silicon carbide single crystal. That is, since the representative p-type impurity boron (B) or aluminum (Al) is a solid material, it is not easy to apply it to the method using a reaction gas.

The present invention is to solve the above problems, by independently controlling the heating and supply of the single crystal raw material and impurities in the manufacturing process of silicon carbide single crystal, to prevent the formation of polycrystals and to grow a silicon carbide single crystal with a uniform impurity content An object of the present invention is to provide a single crystal growing apparatus and a single crystal growing method capable of improving quality.

Another object of the present invention is to prepare a single crystal growth apparatus and a single crystal growth method that can be easily manufactured, especially in the case of using a p-type impurity, which is a solid material, to increase the work efficiency and efficiency. To provide.

In order to achieve the above object, the present invention provides a single crystal raw crucible having seed crystals and single crystal raw materials therein, an impurity crucible connected to the single crystal raw crucible, and provided with impurities therein, and the single crystal raw material crucible and the impurity crucible. It includes a first and second heating means formed respectively on the outside, the first and second heating means provides a single crystal growth apparatus, characterized in that the independent operation by spaced apart. The first and second heating means are characterized in that they comprise a high frequency induction coil.

The single crystal growth phase of the present invention may include an impurity gas supply pipe for transferring the impurity gas from the impurity crucible to the single crystal raw material crucible. Here, the single crystal raw crucible may be provided at an upper portion of the impurity crucible, and the impurity gas supply pipe may extend from an upper surface of the impurity crucible to an internal space through a lower surface of the single crystal raw crucible.

It may also include a carrier gas supply pipe for injecting a carrier gas into the impurity crucible. Here, the carrier gas supply pipe may extend from the outside of the impurity crucible to the inner space through the lower surface of the impurity crucible. Can be formed.

In addition, the single crystal growth lettuce of the present invention may further include a heat insulating material surrounding the crucible and a double quartz tube for cooling surrounding the outside of the heat insulating material, and the heating means may be provided outside the double quartz tube.

The upper or lower portion of the crucible may further include a temperature measuring device, the single crystal raw crucible is characterized in that it comprises a lid which is porous graphite.

The present invention provides a single crystal raw crucible having a seed crystal attached to an upper surface thereof and a single crystal raw material charged therein, preparing an impurity crucible connected to the single crystal raw material and having an impurity loaded therein, and the single crystal raw crucible and the It provides a single crystal growth method comprising the step of simultaneously subliming the single crystal raw material and impurities by heating the impurity crucible independently to grow a single crystal on the seed crystal.

The growing of the single crystal includes maintaining the atmospheric pressure and heating the single crystal raw crucible to a growth temperature, depressurizing to a growth pressure and simultaneously heating the impurity crucible to sublimate the impurity and sublimation on the seed crystal. And reacting the single crystal source gas with the impurity gas to recrystallize it. After subliming the impurity, the method may further include injecting a carrier gas transferring the sublimed impurity gas into the single crystal raw material crucible. In addition, the method may further include purging the inside of the crucible using an unreacted gas.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention in more detail. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention, and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you. Like numbers refer to like elements in the figures.

The single crystal growth of the present invention is carried out by sublimation recrystallization of silicon carbide powder as a raw material on silicon carbide (SiC) single crystals used as seed crystals. At this time, in order to grow a single crystal to which a predetermined impurity is added, the silicon carbide powder is sublimed at the same time as the sublimation, and the seed crystal phase is reacted to recrystallize.

In the single crystal growth apparatus for single crystal growth, the present invention provides a single crystal raw crucible and an impurity crucible separately and forms a means for heating each crucible so that the heating and supply of the single crystal raw material and impurities can be controlled independently. . That is, the single crystal raw material and the impurity gas are uniformly supplied on the seed crystal by making the same sublimation point of the single crystal raw material having different sublimation temperature and the impurity, thereby growing a single crystal having a uniform impurity content.

4 is a cross-sectional view showing a single crystal growth apparatus according to the present invention.

Referring to the drawings, the single crystal growth apparatus is connected to the single crystal raw material crucible 10 and the single crystal raw material crucible 10 having a seed crystal 30 attached thereto and a single crystal raw material A loaded therein. An impurity crucible 40 into which an impurity raw material B is charged, a heat insulating material 70 and a quartz tube 80 surrounding the crucibles 10 and 40, and the single crystal raw material crucible 10 and an impurity crucible outside thereof First and second heating means 90, 100 for heating 40, respectively. In addition, it may further comprise a control device (not shown) for operating the first and second heating means independently.

A carrier gas further includes an impurity gas supply pipe 50 for transferring the impurity gas sublimated from the impurity crucible 40 to the single crystal raw material crucible 10, and injects a carrier gas for smoothly transferring the impurity gas. It further includes a supply pipe (60).

Upper and lower portions of the crucibles 10 and 40 may further include a device capable of measuring temperature.

In addition, the single crystal growth apparatus may further include a supply pipe for injecting a purging gas for the purging process, and may further include a pressure reducing means for reducing the pressure inside the apparatus to the growth pressure during the growth process.

The silicon carbide single crystal of the seed crystal 30 is attached to the inner surface of the lid 20 of the single crystal raw material crucible, and the silicon carbide powder of the single crystal raw material A is charged inside the single crystal raw material crucible 10. The seed crystal 30 may be directly attached to the crucible lid 20, and the seed crystal 30 may be attached to a separate seed crystal holder to prevent the grown single crystal from growing to the crucible upper lid 20. It may be attached and attached to the crucible lid 20. In addition, the impurity (B) added to the single crystal (A) is charged into the impurity crucible 40 disposed separately under the single crystal raw material crucible 10.

The crucibles 10 and 40 are generally cylindrical, but are not necessarily limited to cylindrical, but may be formed in other shapes. The crucibles 10 and 40 are made of a material having a melting point equal to or higher than the sublimation temperature of silicon carbide, and the present embodiment uses a graphite crucible. Alternatively, a material having a melting point above the sublimation temperature of silicon carbide may be applied onto the graphite material. The material to be applied here preferably uses a material which is chemically inert to silicon and hydrogen at the temperature at which the silicon carbide single crystal is grown. For example, metal carbides or metal nitrides may be used, in particular Ta, Hf, Nb, Zr, W, V, and carbides formed of carbon and two or more mixtures thereof, and Ta, Hf, Nb, Zr, W, And among these, nitrides of two or more mixtures and nitrogen can be used.

The lid 20 of the single crystal raw material crucible uses porous graphite. Alternatively, a large amount of holes may be formed in the thin graphite plate. This is to discharge the unreacted impurity gas and the carrier gas to the outside, and serves to control the pressure inside the single crystal raw material crucible 10.

The impurity gas supply pipe 50 for transferring the impurity gas from the impurity crucible 40 to the single crystal raw material crucible 10 has a hollow tube penetrating through an upper surface of the impurity crucible 40 to an upper portion thereof. It is formed through the lower surface of the crucible 10. The impurity gas supply pipe 40 preferably extends to a position higher than a height of silicon carbide powder charged into the single crystal raw material crucible 10.

In addition, the carrier gas supply pipe 60 for injecting the carrier gas in order to facilitate the transfer of the impurity gas is formed through the lower surface of the impurity crucible 40 from the lower portion of the impurity crucible 40. Similarly, the carrier gas supply pipe 60 preferably extends to a position higher than the height of the impurity charged into the impurity crucible 40.

The impurity gas supply pipe 50 and the carrier gas supply pipe 60 can be formed using a graphite tube. The impurity gas sublimated in the impurity crucible 40 is transferred into the single crystal raw material crucible 10 through the impurity gas supply pipe 50 together with the carrier gas injected from the carrier gas supply pipe 60. Thus, the sublimed silicon carbide gas and the impurity gas react to grow a single crystal in which impurities are added on the seed crystal 30.

The outside of the crucible (10, 40) is used to maintain the crystal growth temperature by using a heat insulating material (70). In this case, since the crystal growth temperature of the silicon carbide is very high, the heat insulating material 70 used is a graphite felt made of a tubular cylinder having a predetermined thickness by compressing the graphite fiber. Multiple layers of heat insulating material 70 may be formed around the cylindrical crucibles 10 and 40 to surround the crucibles 10 and 40.

The top or bottom of the crucible (10, 40) may further include a device for measuring the temperature. For example, the center portion of the upper or lower surface of the crucibles 10 and 40 may be exposed without being surrounded by the heat insulating material 70, and the temperature of the upper or lower surfaces of the crucibles 10 and 40 may be measured through the exposed portions. have.

The crucibles 10 and 40 and the heat insulating material 70 described above are disposed inside the cooling double quartz tube 80.

In addition, high frequency induction coils 90 and 100 are installed outside the double quartz tube 80 as heating means for heating the crucibles 10 and 40. By flowing a high frequency current, the crucibles 10 and 40 can be heated and the single crystal raw material A and the impurity B can be heated to a desired temperature. Here, the first high frequency induction coil 90 located outside the single crystal raw material crucible 10 to heat the single crystal raw material A and the seed crystal 3 and the impurity B located outside the impurity crucible 40. ), A second high frequency induction coil 100 for heating. The first high frequency induction coil 90 and the second high frequency induction coil 100 are preferably spaced apart from each other so that thermal alternating current does not occur. The apparatus may further include a control device (not shown) for independently operating the first and second high frequency induction coils.

As such, by placing the high frequency induction coils 90 and 100 outside the single crystal raw material crucible 10 and the impurity crucible 40, heating and supply of the single crystal raw material A and the impurity B can be controlled independently. have. For example, the single crystal raw material (A) is simultaneously heated by first heating a relatively high sublimation temperature (A) and then heating the relatively low sublimation temperature (B) to maintain different sublimation temperatures independently. And the impurity (B) can be sublimed.

In the present embodiment, the single crystal raw crucible 10 and the impurity crucible 40 are disposed in the upper and lower portions, and are connected to each other. However, independent heating control of each crucible 10 and 40 is possible, and the impurity gas is impurity crucible 40. As long as it can smoothly transfer from the single crystal raw material crucible 10, but not limited thereto, the arrangement and connection structure of the crucibles 10 and 40 can be variously formed.

Hereinafter, the single crystal growth method will be described using the above-described single crystal growth apparatus.

First, the seed crystal 30 is attached to the inner surface of the lid 20 of the single crystal raw material crucible, and the single crystal raw material A, for example, silicon carbide powder is charged into the single crystal raw material crucible 10. The seed crystal 30 may be directly attached to the crucible lid 20, and the seed crystal 30 may be attached to a separate seed crystal holder to prevent the grown single crystal from growing to the crucible upper lid 20. It may be attached to the crucible lid 20 by attaching. The lid 20 of the single crystal raw material crucible preferably includes a passage through which unreacted impurity gas and carrier gas can be discharged by using porous graphite or forming a large amount of holes in a thin graphite plate.

In addition, the impurity crucible 40 connected to the single crystal raw material crucible 10 is charged with impurities B such as boron (B) and aluminum (Al).

The single crystal raw crucible 10 and the impurity crucible 40 are mounted in the heat insulating material 70, and then mounted in the double quartz tube 70.

Next, the inside of the apparatus is purged using unreacted gas. In this case, an inert gas may be used as the purging gas, and the present embodiment uses argon (Ar) gas. By purging the air inside the apparatus with argon gas, air remaining in the crucibles 10 and 40 and between the crucibles 10 and 40 and the heat insulating material 70 can be removed.

Thereafter, the raw material purification process corresponding to the heat treatment of the raw material is performed. To this end, the single crystal raw material crucible 10 is heated to 2000 ° C to 2300 ° C through a first high frequency induction coil 90 surrounding the single crystal raw material crucible 10 while maintaining atmospheric pressure. Here, the reason for maintaining the atmospheric pressure is to prevent the occurrence of unwanted crystal polymorphism at the beginning of crystal growth. That is, in the case where the temperature is increased by depressurization from the beginning, when the growth temperature is reached, unwanted crystal polymorphism can be grown.

Therefore, the temperature of the single crystal raw material crucible 10 is first maintained at atmospheric pressure while the temperature of the single crystal raw material crucible 10 is increased to a growth temperature. At the same time, the impurity crucible 40 is heated from 1800 ° C. to 2000 ° C. at a pressure of 20 mbar to 60 mbar through the second high frequency induction coil 100 surrounding the impurity crucible 40 so that the impurity B is sublimed. .

That is, the single crystal raw material (A) having a relatively high sublimation temperature is first heated and then the impurities (B) are heated so that the single crystal raw material (A) and the impurity (B) can be simultaneously sublimed. In addition, by maintaining the temperature of the impurity crucible 40 at an appropriate temperature different from the single crystal raw material crucible 10, the impurity is continuously supplied uniformly.

A carrier gas, for example argon gas (Ar), is injected into the carrier gas supply pipe 60 to transfer the impurity gas sublimed in the impurity crucible 40 to the single crystal raw material crucible 10 through the impurity gas supply pipe 50. Let's do it. Thus, the single crystal source gas and the impurity gas arriving at the seed crystal 30 react on the seed crystal 30 to recrystallize, thereby achieving single crystal growth.

Since the single crystal growth method can independently control the heating of the single crystal raw material crucible and the impurity crucible, it is possible to maintain the temperature of the single crystal raw material and the impurity at different temperatures, and to simultaneously sublimate the single crystal raw material and the impurity having different sublimation temperatures. It is possible to let. Therefore, in the conventional growth process, impurities having a sublimation temperature relatively lower than the growth temperature of the single crystal are excessively sublimed at the beginning of the growth, and as the growth proceeds, the content of impurities rapidly decreases, thereby replacing the impurities of the grown single crystal. It can solve the problem of unevenness. That is, according to the present invention, by separately maintaining the impurity crucible at an appropriate temperature, it is possible to manufacture a single crystal in which impurities are uniformly added to the entire single crystal grown by continuously supplying a certain amount of impurities. In addition, the present invention can sublimate the single crystal raw material and the impurities at the same time, it is possible to prevent the phenomenon that the conventional impurities are first sublimed to form a polycrystal on the seed crystal.

The unreacted impurity gas and the carrier gas are discharged to the outside through the lid 20 of the single crystal raw material crucible made of porous graphite.

After the single crystal of the desired thickness grows on the seed crystal 30, the inside of the apparatus is again maintained at atmospheric pressure to complete the single crystal growth process. In addition, after slowly cooling the temperature, the crucibles 10 and 40 are taken out of the apparatus.

As described above, the single crystal growth method according to the present invention independently controls the heating and supply of the single crystal raw material and the impurity so that the single crystal raw material and the impurity are simultaneously sublimed and the single crystal raw material gas and the impurity gas are constantly supplied on the seed crystal. Thus, the conventional problem that polycrystals are formed on seed crystals can be solved by the impurity sublimation prior to the single crystal raw material, and a single crystal in which impurities are added uniformly can be produced. In addition, according to the present invention, even in the case of a p-type impurity that is a solid material, there is an advantage that can easily grow a single crystal.

As mentioned above, although this invention was demonstrated in detail using the preferable Example, the scope of the present invention is not limited to a specific Example and should be interpreted by the attached Claim. In addition, those skilled in the art should understand that many modifications and variations are possible without departing from the scope of the present invention.

The single crystal growth apparatus and the single crystal growth method according to the present invention can independently control the heating and supply of the single crystal raw material and the impurities during the single crystal growth process, thereby preventing the formation of polycrystals and growing silicon carbide single crystals having a uniform impurity content. This has the advantage of improving quality.

In addition, the silicon carbide single crystal is easy to manufacture, and in particular, even when using a p-type impurity that is a solid material can be easily produced, there is an effect that can increase the work efficiency and efficiency.

Claims (13)

Single crystal raw material crucible which is provided with seed crystal and single crystal raw material therein; An impurity crucible connected to the single crystal raw crucible and provided with impurities therein; And First and second heating means respectively formed outside the single crystal raw material crucible and the impurity crucible, And the first and second heating means are independently operated at predetermined intervals. The method according to claim 1, Wherein said first and second heating means comprise a high frequency induction coil. The method according to claim 1 or 2, And an impurity gas supply pipe for transferring the impurity gas from the impurity crucible to the single crystal raw material crucible. The method according to claim 4, The single crystal raw material crucible is provided on the impurity crucible, And the impurity gas supply pipe extends from an upper surface of the impurity crucible to an inner space through a lower surface of the single crystal raw material crucible. The method according to claim 1 or 2, And a carrier gas supply pipe for injecting a carrier gas into the impurity crucible. The method according to claim 5, And the carrier gas supply pipe extends from an outside of the impurity crucible to an inner space through a lower surface of the impurity crucible. The method according to claim 1 or 2, An insulator surrounding the crucible; And Further comprising a cooling double quartz tube surrounding the outside of the insulation, Single crystal growth apparatus characterized in that the heating means is provided outside the double quartz tube. The method according to claim 1 or 2, Single crystal growth apparatus further comprises a temperature measuring device on the top or bottom of the crucible. The method according to claim 1 or 2, The single crystal raw crucible is a single crystal growth apparatus, characterized in that it comprises a lid which is porous graphite. Preparing a single crystal raw material crucible in which seed crystals are attached to an upper surface and single crystal raw material is charged therein; Providing an impurity crucible connected to the single crystal raw material and containing impurities therein; And And subliming the single crystal raw material and the impurity at the same time by independently heating the single crystal raw material crucible and the impurity crucible to grow the single crystal on the seed crystal. The method according to claim 10, Growing the single crystal, Heating the single crystal raw crucible to a growth temperature while maintaining atmospheric pressure; Sublimating the impurity by heating the impurity crucible while reducing pressure to a growth pressure; And And recrystallizing the monocrystalline raw material gas and the impurity gas sublimated in the seed crystal. The method according to claim 11, After subliming the impurity, And injecting a carrier gas for transferring a sublimed impurity gas into the single crystal raw material crucible. The method according to claim 10, And purging the inside of the crucible using an unreacted gas.

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