WO2022000997A1 - Rare earth element-doped silicon carbide powder - Google Patents

Abstract

A rare earth element-doped silicon carbide powder, comprising a silicon carbide crystal phase and a rare earth element silicide, wherein the rare earth element silicide is doped in the silicon carbide crystal phase. The doping concentration of the rare earth element silicide in the silicon carbide crystal phase is 0.001-5 wt%. In the rare earth element-doped silicon carbide powder, the rare earth element silicide is doped in the silicon carbide crystal phase, so that the rare earth element is uniformly doped in the silicon carbide powder, and during crystal growth, the rare earth element is gradually released along with the sublimation of the silicon carbide powder, thus achieving the uniform doping of the rare earth element in terms of both time and space, and thereby effectively inhibiting the generation of polymorphic defects in the crystal; in addition, the rare earth element silicide is obtained by selecting and using an oxide of the rare earth element with a relatively high purity, so that the production cost of the rare earth element-doped silicon carbide powder is greatly reduced, and the product purity is improved.

Description

A kind of silicon carbide powder doped with rare earth elements technical field

The present application relates to a silicon carbide powder doped with rare earth elements, which belongs to the technical field of semiconductor materials.

Background technique

Silicon carbide (SiC), as a third-generation semiconductor material, is widely used in power electronics, optoelectronic devices and other fields because of its excellent properties such as large band gap, high saturation electron mobility, strong breakdown field, and high thermal conductivity. . High-quality crystals are the cornerstone of the development of semiconductor and information industries, and their preparation level restricts the preparation and performance of downstream devices.

At present, the physical vapor transport (PVT) method is the main method for growing silicon carbide crystals. The equipment used for growing silicon carbide crystals by the physical vapor transport method is simple, and the process is easy to control. However, in the process of growing silicon carbide crystals by PVT method, defects such as dislocations and polytypes will be generated. In the prior art, in order to suppress the generation of polytypes in the growth of silicon carbide crystals, additives are often added in the crystal growth process.

Patent US20090053125A1 discloses that adding Ce silicide or carbide during the growth of 4H-SiC single crystal can suppress the generation of polytype defects. In this patent, CeSi ₂ or CeC ₂ is placed in a small graphite crucible, dispersed and buried in the SiC powder source, sublimated into the gas phase during the crystal growth process, and finally doped into the silicon carbide lattice, thereby promoting the growth of 4H-SiC and inhibit the production of other polytypes. From the process point of view: the silicide or carbide of cerium is placed in a small graphite crucible and then buried in the powder source. The compound of cerium cannot be evenly distributed in the powder, which will inevitably lead to the whole crystal growth process. The inhomogeneous distribution in time and space is also unfavorable for the inhibition of crystal form. In the same way, if the dopant is simply mixed with silicon carbide powder, the dopant does not enter the powder, even if it is uniformly distributed in space, because the melting point and sublimation speed of cerium silicide or carbide and silicon carbide exist. Differences, in the entire crystal growth process, there will still be uneven distribution of time. The introduction of small graphite crucibles is equivalent to the introduction of new variables to the crystal growth system. For the high-purity silicon carbide single crystal growth process, the variables that need to control the purity increase, the process becomes more complicated, and the inhibition effect on polytypes during the growth process of silicon carbide crystals is not ideal.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present application provides a silicon carbide powder doped with rare earth elements. In the silicon carbide powder doped with rare earth elements, the silicide of rare earth elements is doped in the silicon carbide crystal phase. The rare earth elements will be gradually released with the sublimation of the silicon carbide powder, realizing the uniform doping of rare earth elements in time and space, thus effectively suppressing the generation of polytypes.

According to one aspect of the present application, there is provided a rare earth element-doped silicon carbide powder, the rare earth element-doped silicon carbide powder comprising a silicon carbide crystal phase and a rare earth element silicide, the rare earth element silicide doped in the silicon carbide crystalline phase.

Further, the doping concentration of the silicide of the rare earth element in the silicon carbide crystal phase is 0.001-5wt%; preferably, the doping concentration of the silicide of the rare earth element in the silicon carbide crystal phase is 0.005-2.5 wt %; preferably, the doping concentration of the silicide of the rare earth element in the silicon carbide crystal phase is 0.02-0.2 wt %. Further, the lower limit of the doping concentration of the silicide of the rare earth element in the silicon carbide crystal phase is selected from 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt% %, 0.1t%, 0.11wt%, 0.12wt%, 0.13wt%, 0.14wt%, 0.15wt%, 0.16wt%, 0.17wt%, 0.18wt% or 0.19wt%, the silicide of the rare earth element is The upper limit of the doping concentration in the silicon carbide crystal phase is selected from 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt%, 0.08wt%, 0.09wt%, 0.1t%, 0.11wt%, 0.12 wt %, 0.13 wt %, 0.14 wt %, 0.15 wt %, 0.16 wt %, 0.17 wt %, 0.18 wt %, or 0.19 wt %.

Further, the rare earth element is selected from at least one of lanthanides, scandium and yttrium; preferably, the rare earth element is selected from at least one of cerium, lanthanum, praseodymium, neodymium, scandium and yttrium.

Further, the purity of the rare earth element-doped silicon carbide powder is not less than 99.99%; preferably, the purity of the rare earth element-doped silicon carbide powder is not less than 99.999%.

Further, the silicide of the rare earth element is obtained by the following preparation method: the rare earth element-containing substance is reacted with high-purity silicon powder at a high temperature.

Further, the purity of the rare earth element-containing substance is not less than 99.99%, and the rare earth element-containing substance is a solid powder with a particle size of not more than 100 μm. Preferably, the rare earth element-containing substance is an oxide of a rare earth element. Preferably, the molar ratio of the rare earth element in the rare earth element-containing substance to the high-purity silicon powder is 1:2 to 4, and preferably, the molar ratio of the doped rare-earth element to the high-purity silicon powder is 1:2 ~3.

In the silicon carbide powder doped with rare earth elements of the present application, silicides of rare earth elements are prepared by selecting oxides of rare earth elements. In comparison, commercially available silicides and carbides of rare earth elements (commercially available The silicides and carbides of rare earth elements have high prices and low purity), which greatly reduces production costs and improves product purity.

Further, the conditions of the high-temperature reaction are: the rare earth element-containing substance and the high-purity silicon powder are reacted under vacuum conditions at a temperature of 1400-1800° C. for 1-5 hours; preferably, the conditions of the high-temperature reaction are: Rare earth element substances and high-purity silicon powder are ^{reacted for 2-4 hours at a pressure not higher than 10 -2} Pa and a temperature of 1500-1600°C.

Further, the silicon carbide powder doped with rare earth elements is agglomerated particles, the particle size of the agglomerated particles is not greater than 2 mm, the particle size of the single crystal grains in the agglomerated particles is not greater than 500 μm, and the rare earth element doped particles are not larger than 500 μm. The bulk density of the silicon carbide powder is 0.7-1.1 g/cm ³ .

According to another aspect of the present application, there is also provided the preparation method of the rare earth element-doped silicon carbide powder according to any one of the above, the preparation method comprising the steps of: silicide of rare earth element, high-purity silicon carbide The powder and high-purity carbon powder are obtained by reacting at least 5 hours at a temperature of 1100-1600 °C under vacuum conditions.

In the preparation method of the present application, the silicide of rare earth element, high-purity silicon powder and high-purity carbon powder are reacted under high temperature and vacuum. First, the high-purity carbon powder and high-purity carbon powder react to form silicon carbide, and then the silicide of rare earth element is doped The hetero-packaging is carried out in the silicon carbide crystal phase, so that the rare earth element and the silicon carbide crystal phase are uniformly doped, that is, the rare earth element is doped in the raw material synthesis stage of the silicon carbide powder. When using the rare earth element-doped silicon carbide powder to grow crystals, the rare earth elements in the silicon carbide powder will be gradually released along with the sublimation of the powder during the growth process, so as to achieve uniform doping in time and space and ensure crystal growth. The process can effectively suppress polytypes from beginning to end.

Further, the mass ratio of the sum of the mass of the high-purity carbon powder and the high-purity silicon powder to the silicide of the rare earth element is 100:0.001-5. Preferably, the mass ratio of the sum of the mass of the high-purity carbon powder and the high-purity silicon powder to the silicide of the rare earth element is 100:0.005-2.5, and the molar ratio of the high-purity carbon powder and the high-purity silicon powder is 1～2.5. 1.5:1. Preferably, the particle size of the high-purity silicon powder and the high-purity carbon powder is not greater than 100 μm; the purity of the high-purity carbon powder and the high-purity silicon powder is not less than 99.9%.

Further, the preparation method includes the following steps: 1. The rare earth element-doped silicide, high-purity silicon powder and high-purity carbon powder are reacted for 5-15 hours at a pressure not higher than 10 ^-2 Pa and a temperature of 1200-1400° C. , to obtain β-type silicon carbide powder doped with rare earth elements.

Further, the preparation method further includes the following steps: (2) at the temperature of step (1), filling a protective gas, raising the temperature to 2000-2500 °C, and reacting for at least 10 hours to obtain α-type silicon carbide powder doped with rare earth elements; Preferably, the conditions of the synthesis reaction further include the following steps: ② at the temperature of step ①, charging a protective gas to a pressure of 500-1000 mbar, raising the temperature to 2200-2400 °C, and reacting for 10-40 h to obtain the doping Rare earth element α-type silicon carbide powder; preferably, the protective gas is a mixed gas of inert gas and hydrogen, and the volume fraction of hydrogen in the mixed gas is 2-3%. Hydrogen is mainly used to inhibit the carbonization of silicon carbide powder, so that the atmosphere in the crucible is evenly distributed.

According to another aspect of the present application, there is also provided the rare earth element doped silicon carbide powder according to any one of the above or the rare earth element doped silicon carbide powder prepared by the preparation method according to any one of the above. Applications in the preparation of high-quality silicon carbide crystals. Since the rare earth element doped silicon carbide powder or the rare earth element doped silicon carbide powder prepared by the preparation method is uniformly doped and has high purity, it is used as a raw material for silicon carbide crystals. During growth, the obtained silicon carbide crystal not only has high purity, but also has few defects, and the quality of the crystal is high.

The beneficial effects of this application include but are not limited to:

(1) Silicon carbide powder doped with rare earth elements in the present application, the silicide of rare earth elements is doped in the silicon carbide crystal phase, so that the rare earth elements are uniformly doped in the silicon carbide powder. The sublimation of silicon carbide powder is gradually released, and the uniform doping of rare earth elements in time and space is realized, thereby effectively suppressing the generation of polytype defects in the crystal.

(2) Silicon carbide powder doped with rare earth elements in the present application, select oxides of rare earth elements with higher purity to obtain silicides of rare earth elements, and then dope the silicides of rare earth elements into the silicon carbide crystal phase, the The doped rare earth element raw material has high purity and low cost, greatly reduces the production cost of the rare earth element doped silicon carbide powder, and at the same time improves the product purity.

(3) The preparation method of the present application is simple, the conditions are easy to control, and the prepared silicon carbide powder doped with rare earth elements is not only uniformly doped with rare earth elements, but also has high purity.

(4) The rare earth element in the silicon carbide powder doped with rare earth elements of the present application is uniformly doped with high purity. higher.

detailed description

The present application will be described in detail below with reference to the examples, but the present application is not limited to these examples.

Unless otherwise specified, the raw materials and the like involved in the examples of the present application are all purchased through commercial channels.

Example 1

This embodiment provides a rare earth element doped silicon carbide powder, the rare earth element doped silicon carbide powder includes a silicon carbide crystal phase and a rare earth element silicide, and the rare earth element silicide is doped in in the crystalline phase of silicon carbide.

The doping concentration of the silicide of the rare earth element in the silicon carbide crystal phase is 0.001-5 wt %; preferably, the doping concentration of the silicide of the rare earth element is 0.005-2.5 wt %. More preferably, the doping concentration of the silicide of the rare earth element in the silicon carbide crystal phase is 0.02-0.2 wt %.

The rare earth element is selected from at least one of lanthanides, scandium and yttrium; preferably, the rare earth element is selected from at least one of cerium, lanthanum, praseodymium, neodymium, scandium and yttrium. More preferably, the rare earth element is cerium.

The purity of the rare earth element doped silicon carbide powder is not less than 99.99%; preferably, the purity of the rare earth element doped silicon carbide powder is not less than 99.999%. The silicon carbide powder doped with rare earth elements is agglomerated particles, the particle size of the agglomerated particles is not more than 2 mm, and the particle size of the single crystal grains in the agglomerated particles is not more than 500 μm. The bulk density of the agglomerated particles is 0.7-1.1 g/cm ³ , and the bulk density after compaction is 1.1-2.0 g/cm ³ .

Example 2

The present embodiment provides a method for preparing the above-mentioned rare-earth element-doped silicon carbide powder, which includes the following steps:

(1) The rare earth element-containing material is uniformly mixed with the high-purity silicon powder, wherein the rare earth element-containing material is selected from powdered cerium (Ce) and other lanthanides (lanthanum La, praseodymium Pr, neodymium Nd, etc.) or At least one of the oxides of yttrium Y and scandium Sc; the oxide of the rare earth element is a solid powder with a particle size of not more than 100 μm, and the purity is not less than 99.99%; the doped rare earth element and high-purity silicon powder The molar ratio of the doped rare earth element to the high-purity silicon powder is 1:1.5-2.5; preferably, the molar ratio of the doped rare earth element to the high-purity silicon powder is 1:1.8-2.2;

(2) The mixture in step (1) is heated to 1400-1800° C. under vacuum conditions for 1-5 hours. At this temperature, the high-purity silicon powder can react with the oxides of the above rare earth elements to obtain doped rare earth elements. The silicide; preferably, the reaction temperature is 1500～1600℃, the pressure is not higher than 10 ^-2 Pa, and the reaction time is 2～4h;

(3) ① Evenly mix the rare earth element-doped silicide, high-purity silicon powder and high-purity carbon powder in step (2), the sum of the mass of the high-purity carbon powder and high-purity silicon powder is the same as that of the rare-earth element-doped silicide. The mass ratio of the silicide is 100:0.001-5; preferably, the mass ratio of the sum of the mass of the high-purity carbon powder and the high-purity silicon powder to the mass ratio of the silicide doped with rare earth elements is 100:0.005-2.5;

The above mixture is at a reaction temperature of 1100-1600°C, a pressure not higher than 10 ^-2 Pa, and a reaction time of 5-15h, wherein the molar ratio of the high-purity carbon powder and the high-purity silicon powder is 1-1.5:1, Obtaining β-type silicon carbide powder doped with rare earth elements;

In the step ① ② temperature, charged with shielding gas, raising the temperature to 2000 ~ 2500 ℃, the pressure was 500 ~ 1000mbar, the reaction time is 10 ~ 40h; protective gas is an inert gas into a mixed gas of H ₂ and the volume fraction of mixed gas of H ₂ 2 to 3 percent, the inert gas is selected from argon and / or helium, to obtain rare-earth doped α-type silicon carbide powder.

The silicon carbide powder doped with rare earth elements is prepared according to the above method, and the difference from the above preparation method is shown in Table 1. Silicon powder 4#, contrast silicon carbide powder D1#, contrast silicon carbide powder D2#, contrast silicon carbide powder D3#. Among them, the purity of high-purity carbon powder, high-purity silicon powder and oxides of rare earth elements is greater than 99.99%, and the filled protective gas is a mixed gas of argon gas and hydrogen gas.

Table 1

The silicon carbide powder 1#, silicon carbide powder 2#, silicon carbide powder 3#, silicon carbide powder 4#, comparative silicon carbide powder D1#, comparative silicon carbide powder D2# and comparative silicon carbide powder D3# prepared above were used. Characterize. And the silicon carbide crystal is grown by using the above silicon carbide powder, and the polytype of the grown crystal is detected. The detection results are shown in Table 2.

Table 2

It can be seen from the results in Table 2 that the rare earth element-doped silicon carbide powder prepared in the present application is a pale yellow-white agglomerated particle, the rare earth element in the powder is more uniformly doped, and the purity is high, and the total impurity content does not exceed 10ppm, The purity is not less than 99.999%. Compared with the comparative silicon carbide powders D1# to D3#, the rare earth element-doped silicon carbide powder of the present application is more uniform in doping, with low impurity content and high purity.

Use the method provided in this application to synthesize silicon carbide powder 1'#, silicon carbide powder 2'# and silicon carbide powder 3'#, silicon carbide powder 1'#, silicon carbide powder 2'# and carbide powder of cerium doped silicon carbide powder The mass ratio of silicon powder 3'# medium and high-purity carbon silicon powder to cerium silicide is 100:0.004. Silicon carbide powder 1#, silicon carbide powder 2#, and silicon carbide powder 3# are respectively used for the growth of silicon carbide crystals. In the crystal growth crucible, sample silicon carbide powder 1'# at a distance of 80mm from the crucible mouth, sample silicon carbide powder 2'# at a distance of 90mm from the crucible mouth, and sample silicon carbide powder 3'# at a distance of 100mm from the crucible mouth.

Comparative silicon carbide powder D1'#, comparative silicon carbide powder D2'#, and comparative silicon carbide powder D3'# are respectively after mechanical mixing of silicon carbide powder and cerium silicide (the sum of the mass of The mass ratio of cerium silicide is 100:0.004) for the growth of silicon carbide crystals. The comparison silicon carbide powder D1'# is sampled at a distance of 80mm from the crucible mouth in the growth crucible, and the comparison silicon carbide powder D2'# is 90mm away from the crucible mouth. Sampling, the comparative silicon carbide powder D3'# is sampled at a distance of 100mm from the crucible mouth.

The comparative silicon carbide powder R1#, the comparative silicon carbide powder R2#, and the comparative silicon carbide powder R3# are respectively placed cerium silicide in a small graphite crucible (the sum of the mass of the high-purity silicon carbide powder and the mass ratio of the cerium silicide in the small crucible is 100:0.004), buried in the silicon carbide powder for the growth of silicon carbide crystals, the comparative silicon carbide powder R1# was sampled in the same crystal growth crucible at a distance of 80 mm from the crucible mouth, and the comparative silicon carbide powder was sampled at a distance of 90 mm from the crucible mouth. R2# is sampled, and the silicon carbide powder R3# is sampled at a distance of 100mm from the crucible mouth.

Silicon carbide powder 1'#, silicon carbide powder 2'#, silicon carbide powder 3'#, comparative silicon carbide powder D1'#, comparative silicon carbide powder D2'#, comparative silicon carbide powder D3'#, comparative carbonization powder using GDMS The concentration of cerium (Ce) in the samples of silicon powder R1#, comparative silicon carbide powder R2#, and comparative silicon carbide powder R3# was detected, and the polytype area of the crystal rod grown from the silicon carbide powder raw material was detected. The results as shown in Table 3.

table 3

As can be seen from the results in Table 3, the Ce concentration in the raw material before the crystallization reaction is approximately equal to the Ce concentration in the raw material (because cerium silicide is not completely uniformly mixed in the raw material, and the height of the raw material is different, resulting in different Ce concentration results. ); while the cerium silicide was embedded in the silicon carbide powder with a small crucible, no Ce could be detected in the comparative silicon carbide powder R1#~R3#. The crystal growth is carried out for 20 hours. Since the cerium silicide of the present application is doped into the silicon carbide crystal phase, the cerium is released evenly and slowly; the method of directly mixing the cerium silicide and the silicon carbide raw materials is due to the low melting point of the cerium silicide and volatilizes quickly. The Ce concentration in the small crucible decreases rapidly; the cerium silicide buried in the small crucible gradually diffuses into the silicon carbide raw material, but the concentration is low, and the farther away from the small crucible, the harder it is to detect. At the end of the crystal growth, since the cerium silicide of the present application is doped into the silicon carbide crystal phase, the residual cerium dopant in the raw material can still be detected after the reaction is completed. In the direct mixing method, the cerium silicide volatilizes quickly in the early stage, and the reaction There is little residue left in the raw material. The cerium silicide in the small crucible diffuses out, and the closer it is to the small crucible, the higher the concentration. In summary, the cerium silicide in the raw material of the present application is uniformly volatilized, and the crystal rod has no polymorphism; the cerium silicide and the silicon carbide powder are directly mixed, a large amount of cerium silicide volatilizes in the early stage, and the cerium silicide is insufficient in the later stage, and polytypes are easily generated in the later stage; the cerium silicide is buried In the crucible, the lack of cerium silicide in the early stage is easy to produce polytypes.

The above are only the embodiments of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. Various modifications and variations of this application are possible for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application shall be included within the protection scope of the present application.

Claims (13)

A rare earth element doped silicon carbide powder, characterized in that the rare earth element doped silicon carbide powder comprises a silicon carbide crystal phase and a rare earth element silicide, and the rare earth element silicide is doped in the carbide in the silicon phase. The rare earth element-doped silicon carbide powder according to claim 1, wherein the doping concentration of the rare earth element silicide in the silicon carbide crystal phase is 0.001-5wt%. The silicon carbide powder doped with rare earth elements according to claim 1, wherein the doping concentration of the silicide of rare earth elements in the silicon carbide crystal phase is 0.005-2.5 wt%. The rare earth element-doped silicon carbide powder according to claim 1, wherein the rare earth element is selected from at least one of lanthanides, scandium and yttrium. The rare earth element-doped silicon carbide powder according to claim 1, wherein the rare earth element is selected from at least one of cerium, lanthanum, praseodymium, neodymium, scandium and yttrium. The rare earth element-doped silicon carbide powder according to claim 1, wherein the purity of the rare earth element-doped silicon carbide powder is not less than 99.99%. The rare earth element-doped silicon carbide powder according to claim 1, wherein the purity of the rare earth element-doped silicon carbide powder is not less than 99.999%. The rare-earth element-doped silicon carbide powder according to claim 1, wherein the rare-earth element silicide is obtained by the following preparation method: performing a high-temperature reaction between a rare-earth element-containing substance and high-purity silicon powder to obtain . The rare earth element-doped silicon carbide powder according to claim 8, wherein the purity of the rare earth element-containing material is not less than 99.99%, and the rare earth element-containing material is a solid powder with a particle size of not more than 100 μm . The rare earth element-doped silicon carbide powder according to claim 8, wherein the rare earth element-containing substance is an oxide of a rare earth element. The rare earth element-doped silicon carbide powder according to claim 8, wherein the molar ratio of the rare earth element in the rare earth element-containing substance to the high-purity silicon powder is 1:2-4. The silicon carbide powder doped with rare earth elements according to claim 8, characterized in that, the conditions for the high temperature reaction are as follows: the rare earth element-containing material and the high-purity silicon powder are subjected to vacuum conditions at a temperature of 1400-1800° C. The reaction is carried out for 1 to 5 hours. The rare earth element-doped silicon carbide powder according to claim 8, wherein the conditions for the high temperature reaction are: the rare earth element-containing material and the high-purity silicon powder are ^{subjected to a pressure not higher than 10 -2} Pa, a temperature of 1500～1600℃, reaction 2～4h.