CN116145258A - Method for growing SiC crystal by low-temperature solution method - Google Patents

Abstract

The invention relates to a method for growing SiC crystals by a low-temperature solution method, and belongs to the technical field of crystal growth. Mix high-purity silicon, metal Fe or Cr, and rare earth metals for alloying and melting. The melting time is 5-30 minutes to obtain Si-Me-RE alloy with uniform composition; Si-Me-RE alloy is loaded into the crystal growth furnace In a high-purity dense graphite crucible or SiC crucible, keep the melting temperature higher than 1823K for at least 1 hour to dissolve C or SiC into the high-temperature melt to obtain SiMe-RE-C melt saturated with SiC; Si‑Me‑RE‑C melts are used for solution growth of SiC single crystal or polycrystalline SiC. The method for growing SiC crystals by the low-temperature solution method provided by the present invention solves the problem of low solubility of C or SiC when growing SiC crystals by the solution method, and can greatly increase the solubility of Si melts at low temperatures (at least 400K lower than the existing PVT method). The solubility of C or SiC is a low-energy, low-cost, high-efficiency, and pollution-free method for growing SiC crystals.

Description

A kind of method for growing SiC crystal by low temperature solution method

technical field

The invention relates to a method for growing SiC crystals by a low-temperature solution method, and belongs to the technical field of crystal growth.

Background technique

SiC single crystal is a new generation of electronic core material, which is mainly used as the core substrate material of the third generation wide band gap and high power semiconductor devices. Compared with the first-generation and second-generation semiconductor materials, SiC single crystal has the characteristics of high temperature resistance, high pressure, high power, and radiation resistance, and can be used to manufacture high-speed, high-frequency operation in harsh environments such as high temperature, high pressure, and strong radiation. high-power devices.

At present, the physical vapor transport method is the mainstream technology for the industrial production of SiC single crystals at home and abroad, but the method produces SiC single crystals with low yield, high growth temperature, and high energy consumption, resulting in high production costs and the grown SiC single crystals Accompanied by defects such as micropipes, which affect its material properties. In addition, the physical vapor transport method is to decompose the SiC raw material into a complex mixed gas phase at ultra-high temperature, but the mixed gas phase reaction obtained by sublimation is more complicated, and the crystal growth process is difficult to control. Therefore, the price of SiC single crystal grown by physical vapor transport method is relatively expensive at present, which limits the popularization and use of SiC single crystal in semiconductor devices.

The solution method is another method for growing SiC single crystals. At present, this method can obtain low defect density and high-quality SiC single crystals under laboratory conditions. The solution method can realize the growth of high-quality SiC single crystals in a state of near thermodynamic equilibrium. This method has the advantages of fewer crystal microtubules, stronger controllability of the growth process, and easy realization of p-type doping. When SiC single crystal is grown by solution method, the solubility of C in silicon melt is the key factor to determine the growth rate of SiC single crystal, but the solubility of C in silicon melt below 2273K is very low, which limits the solubility of C in silicon melt. Therefore, it is difficult to achieve rapid growth of SiC single crystals using pure silicon melts. How to improve the solubility of C in silicon melts is a technical problem that needs to be solved for rapid growth of SiC single crystals at low temperatures.

Aiming at the problem of low C solubility when growing SiC single crystals by the solution method, the researchers proposed a method of adding a cosolvent to the silicon melt to increase the C solubility in the melt. This solution method of adding a co-solvent is called a co-solvent method. In addition, the added co-solvent can form a low melting point melt with silicon, so the co-solvent method is also a technique for growing SiC single crystal at low temperature. The co-solvents that have been reported so far mainly include chromium, titanium, iron, cobalt and so on. Compared with pure silicon melt, when these co-solvents are used, the solubility of C can be significantly improved, which is beneficial to the growth of SiC single crystal at low temperature, but the solubility of C in the melt is still limited. Therefore, it is necessary to continue to develop new co-solvents to increase the solubility of C in silicon melts to solve the problem of limited growth rate of SiC single crystals. On the other hand, high-purity polycrystalline SiC is an important raw material for growing SiC single crystals. When the method of recrystallization is used to purify polycrystalline SiC, it also faces the problem that the solubility of SiC in the melt is too low, and the method of recrystallization cannot be used to purify polycrystalline SiC. In summary, no matter whether the solution method is used to grow SiC single crystals or the method of recrystallization is used to prepare high-purity polycrystalline SiC crystals, it is necessary to solve the problem of low solubility of SiC in silicon melts, and it is necessary to develop new co-solvents to improve silicon C or SiC solubility in the melt.

Contents of the invention

Aiming at the above-mentioned problems in the prior art, the present invention provides a method for growing SiC crystals by a low-temperature solution method. The invention can greatly increase the solubility of C in silicon melt under low temperature conditions, and provides the possibility for rapid growth of high-quality SiC single crystal and polycrystalline SiC by solution method at low temperature. The method solves the technical problem of low solubility of C in the silicon melt. The present invention is realized through the following technical solutions.

A method for growing SiC crystals by a low-temperature solution method, comprising the following steps:

Step 1. Mix high-purity silicon, metal Fe or Cr (Me), and rare earth metal (RE) for alloying and melting. The melting time is 5-30 minutes to obtain Si-Me-RE alloy with uniform composition. The melting atmosphere is normal pressure or High-purity inert gas under negative pressure (purity>99.999%), the melting temperature is higher than the melting point of Si-Me-RE alloy, and the alloying melting method adopts water-cooled copper crucible technology or electromagnetic levitation melting technology, preferably water-cooled copper crucible technology.

Step 2. Put the Si-Me-RE alloy obtained in step 1 into a high-purity dense graphite crucible or SiC crucible in a crystal growth furnace, and keep the temperature above 1823K for at least 1 hour to make C or SiC go to high temperature SiC-saturated Si-Me-RE-C melt is obtained by dissolving in the melt; the melting atmosphere is a high-purity inert gas or a mixed gas of hydrogen and high-purity inert gas, and the volume content of hydrogen in the mixed gas is ≤10%;

Step 3. The SiC-saturated Si-Me-RE-C melt obtained in step 2 is subjected to solution growth of SiC single crystal or polycrystalline SiC; the crystal growth method is a conventional crystal growth method, including but not limited to top seed crystal solution growth method or crucible descent method, the crystal growth temperature is higher than 1823K, the SiC crystal growth atmosphere is a high-purity inert gas (purity >99.999%) or a mixed gas of hydrogen and high-purity inert gas, and the hydrogen volume content in the mixed gas is ≤10%.

The content of Me in the Si-Me-RE alloy in the step 1 is ≤45 at.%, Me represents one or both of Fe or Cr; the total content of RE is ≤35 at.%, and RE represents one of the rare earth metals or several kinds; under the above conditions, adjust the ratio of Me, RE and Si so that the total content of Me, RE and Si is 100 at.%.

The mixture of metal Fe or Cr and rare earth metal in the step 1 is a cosolvent; the rare earth metal is one or more of the rare earth elements, including scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce ), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm ), ytterbium (Yb), lutetium (Lu) or a mixture of any proportion.

In the above step 3, the crystal growth conditions other than temperature are not limited, that is, the temperature gradient, the type of SiC seed crystal, the rotation speed of the seed rod or crucible, and the heating method of the crystal furnace (electromagnetic induction or resistance heating) are not limited.

The beneficial effects of the present invention are:

(1) The present invention provides a new co-solvent method to improve the solubility of C or SiC in silicon melt, that is, the mixed metal of Me+RE is used as a co-solvent, which solves the problem of low solubility of C or SiC when growing SiC crystals by low-temperature solution method ;

(2) The co-solvent for growing SiC crystals by the low-temperature solution method proposed by the present invention can not only be used to grow SiC single crystals, but also can be used as a material for preparing high-purity polycrystalline SiC;

(3) When rare earth is used as a cosolvent, since the rare earth melts before silicon, the molten rare earth first reacts with the crucible to form rare earth carbides, which affects the quality of growing SiC crystals; the present invention solves this problem by using a pre-melted alloy ;

(4) When rare earths are used as auxiliary solvents, rare earths are easy to react with a small amount of oxygen in the furnace, reducing the solubility of SiC in the melt; the invention solves the problem by mixing hydrogen and inert gases (hydrogen content ≤ 10%) this problem;

(5) The present invention is a technology for growing SiC crystals with low energy consumption, no pollution, and low cost;

(6) The method for growing SiC crystals by the low-temperature solution method provided by the present invention solves the problem of low solubility of C or SiC when growing SiC crystals by the solution method, and can greatly increase Si at low temperature (at least 400K lower than the existing PVT method). The solubility of C or SiC in the melt is a low-energy, low-cost, high-efficiency, and pollution-free method for growing SiC crystals.

Description of drawings

Fig. 1 is a schematic flow chart of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Example 1

As shown in Figure 1, the method for growing SiC crystals by the low-temperature solution method comprises the following steps:

Step 1. Mix high-purity silicon (purity 99.9999wt%), metal Cr (purity 99.99wt%), and rare earth metal Nd (purity 99.9wt%) for alloying and melting. The melting time is 5 minutes to obtain 50at.% Si with uniform composition -35at.%Cr-15at.%Nd alloy, the melting atmosphere is high-purity inert gas (argon, purity>99.999wt%) under negative pressure, and the melting temperature is higher than 50at.%Si-35at.%Cr-15at. The melting point of the %Nd alloy, the alloying melting method is an electric arc furnace melting technology with a water-cooled copper crucible;

Step 2, put the 50at.%Si-35at.%Cr-15at.%Nd alloy obtained in step 1 into the high-purity dense graphite crucible in the crystal growth furnace, and keep it warm for 1 hour when the melting temperature is 1823K, so that C Dissolve in high temperature melt to obtain SiC saturated Si-Cr-Nd-C melt (C content is 4.44 wt.%); melting atmosphere is high-purity argon (99.999wt%) + 10%H ₂ mixed gas;

Step 3, in the SiC saturated Si-Cr-Nd-C melt obtained in step 2, perform solution growth of SiC single crystal; the crystal growth method is the top seed crystal solution growth method, the crystal growth temperature is 1823K, and the SiC crystal growth atmosphere is It is a mixed gas of high-purity argon (99.999wt%) + 10% H ₂ .

Example 2

As shown in Figure 1, the method for growing SiC crystals by the low-temperature solution method comprises the following steps:

Step 1. Mix high-purity silicon (purity 99.9999wt%), metal Fe (purity 99.99wt%), and rare earth metal Pr (purity 99.9wt%) for alloying and melting. The melting time is 6 minutes to obtain 50at.% Si with uniform composition -15at.%Fe-35at.%Pr alloy, the melting atmosphere is high-purity inert gas (argon, purity>99.999wt%) under negative pressure, and the melting temperature is higher than 50at.%Si-15at.%Fe-35at. The melting point of the %Pr alloy, the alloying melting method is an electric arc furnace melting technology with a water-cooled copper crucible;

Step 2, put the 50at.%Si-15at.%Fe-35at.%Pr alloy obtained in step 1 into the SiC crucible in the crystal growth furnace, and keep it warm for 1 hour when the melting temperature is 1923K, so that SiC is melted at high temperature SiC saturated Si-Fe-Pr-C melt (C content is 6.78 wt.%) is obtained by dissolving in the body; the melting atmosphere is high-purity argon (99.999wt%);

Step 3, in the SiC-saturated Si-Fe-Pr-C melt obtained in step 2, perform solution growth of SiC single crystal; the crystal growth method is the top seed crystal solution growth method, the crystal growth temperature is 1923K, and the SiC crystal growth atmosphere is It is a high-purity inert gas (argon, purity >99.999%).

Example 3

As shown in Figure 1, the method for growing SiC crystals by the low-temperature solution method comprises the following steps:

Step 1. Mix high-purity silicon (purity 99.9999wt%), metal Fe (purity 99.99wt%), and rare earth metal La (purity 99.9wt%) for alloying and melting. The melting time is 10 minutes to obtain 50at.% Si with uniform composition -45at.%Fe-5at.%La alloy, the melting atmosphere is high-purity inert gas (argon, purity>99.999wt%) under negative pressure, and the melting temperature is higher than 50at.%Si-45at.%Fe-5at. The melting point of the %La alloy, the alloying melting method is an electric arc furnace melting technology with a water-cooled copper crucible;

Step 2, put the 50at.%Si-45at.%Fe-5at.%La alloy obtained in step 1 into the SiC crucible in the crystal growth furnace, and keep it warm for 1.5 hours when the melting temperature is 1923K, so that SiC is melted at high temperature SiC-saturated Si-Fe-La-C melt (C content is 0.4wt.%) is obtained by dissolving in the body; the melting atmosphere is high-purity helium (99.999wt%) + 10%H ₂ mixed gas;

Step 3. In the SiC-saturated Si-Fe-La-C melt obtained in step 2, perform solution growth of SiC single crystal; the crystal growth method is the top seed crystal solution growth method, the crystal growth temperature is 1923K, and the SiC crystal growth atmosphere is The melting atmosphere is a mixed gas of high-purity helium (99.999wt%) + 10% H ₂ .

Example 4

As shown in Figure 1, the method for growing SiC crystals by the low-temperature solution method comprises the following steps:

Step 1, the mixture of high-purity silicon (purity 99.9999wt%), metal Fe (purity 99.99wt%), rare earth metal Y and Pr (the purity of Y and Pr are both 99.9wt%, the mass ratio of Y and Pr is 1 :20) After mixing, carry out alloy melting, and the melting time is 10 minutes to obtain 60at.%Si-10at.%Fe-30at.%(Y+Pr) alloy with uniform composition. The melting atmosphere is high-purity inert gas under negative pressure (argon gas, purity>99.999wt%), the melting temperature is higher than the melting point of 60at.%Si-10at.%Fe-30at.%(Y+Pr), and the alloying melting method is an electric arc furnace melting technology with a water-cooled copper crucible;

Step 2, put the 60at.%Si-10at.%Fe-30at.%(Y+Pr) alloy obtained in step 1 into the high-purity dense graphite crucible in the crystal growth furnace, and keep it warm for 1.5 hours when the melting temperature is 1923K hours, dissolve C into the high-temperature melt to obtain SiC-saturated Si-Fe-(Y+Pr)-C melt (C content is 3.23 wt.%); the melting atmosphere is high-purity helium (99.999wt%)+ 10%H ₂ mixed gas;

Step 3, in the SiC-saturated Si-Fe-(Y+Pr)-C melt obtained in step 2, perform solution growth of SiC single crystal; the crystal growth method is the top seed crystal solution growth method, and the crystal growth temperature is 1923K, The SiC crystal growth atmosphere is a smelting atmosphere of high-purity helium (99.999wt%) + 10% H ₂ mixed gas.

Example 5

Step 1. After mixing high-purity silicon (purity 99.9999wt%), metal Fe and Cr (both with a purity of 99.99wt%, and the mass ratio of Fe to Cr is 4:3), and rare earth metal La (both 99.9wt%) Carry out alloy melting, the melting time is 10min to obtain 50at.%Si-35at.%(Fe+Cr)-15at.%La alloy with uniform composition, and the melting atmosphere is high-purity inert gas under negative pressure (argon, purity>99.999 wt%), the melting temperature is higher than the melting point of 50at.%Si-35at.%(Fe+Cr) -15at.%La alloy, and the alloying melting method is electric arc furnace melting technology with water-cooled copper crucible;

Step 2, put the 50at.%Si-35at.%(Fe+Cr)-15at.%La alloy obtained in step 1 into the high-purity dense graphite crucible in the crystal growth furnace, and keep it warm for 1.5 hours when the melting temperature is 1823K hours, dissolve C into the high-temperature melt to obtain SiC-saturated Si-(Fe+Cr)-La-C melt (C content is 2.4 wt.%); the melting atmosphere is high-purity helium (99.999wt%)+ 10%H ₂ mixed gas;

Step 3, in the SiC saturated Si-(Fe+Cr)-La-C melt obtained in step 2, carry out the solution method to grow SiC polycrystalline; the crystal growth method is the crucible drop method, the crystal growth temperature is 1823K, and the SiC crystal grows The atmosphere is a smelting atmosphere of high-purity helium (99.999wt%) + 10% H ₂ mixed gas.

The specific embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Variations.

Claims (3)

1. A method for growing SiC crystals by low-temperature solution method, characterized in that it may further comprise the steps: Step 1. Mix high-purity silicon, metal Fe or Cr, and rare earth metals for alloying and smelting. The smelting time is 5-30 minutes to obtain a Si-Me-RE alloy with uniform composition. Inert gas, the melting temperature is higher than the melting point of Si-Me-RE alloy, and the alloying melting method adopts water-cooled copper crucible technology or electromagnetic levitation melting technology; Step 2. Put the Si-Me-RE alloy obtained in step 1 into a high-purity dense graphite crucible or SiC crucible in a crystal growth furnace, and keep the temperature above 1823K for at least 1 hour to make C or SiC go to high temperature SiC-saturated Si-Me-RE-C melt is obtained by dissolving in the melt; the melting atmosphere is a high-purity inert gas or a mixed gas of hydrogen and high-purity inert gas, and the volume content of hydrogen in the mixed gas is ≤10%; Step 3, in the SiC saturated Si-Me-RE-C melt obtained in step 2, perform solution growth of SiC single crystal or polycrystalline SiC; the crystal growth method is a conventional crystal growth method, including but not limited to the top seed crystal solution Growth method or crucible descent method, the crystal growth temperature is higher than 1823K, the SiC crystal growth atmosphere is a high-purity inert gas or a mixed gas of hydrogen and high-purity inert gas, and the hydrogen volume content in the mixed gas is ≤10%. 2. The method for growing SiC crystals by low-temperature solution method according to claim 1, characterized in that: the content of Me in the Si-Me-RE alloy in the step 1 is ≤45 at.%, and Me represents one of Fe or Cr One or two kinds; the total content of RE ≤ 35at.%, RE represents one or several rare earth metals; under the above conditions, adjust the ratio of Me, RE and Si so that Me, RE and Si The total content of the three is 100 at.%. 3. The method for growing SiC crystals by low-temperature solution method according to claim 1, characterized in that: the mixture of metal Fe or Cr and rare earth metals in the step 1 is a cosolvent; the rare earth metals are one or more of the rare earth elements Several kinds, including scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium or a mixture of several in any proportion.

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