JP6655265B2 - Method and apparatus for producing Mg2Si1-xSnx crystal - Google Patents

Description

The present invention relates to a method and an apparatus for manufacturing a Mg ₂ Si _1-x Sn _x crystal used for a material of an infrared sensor.

  In recent years, as autonomous driving functions are installed in automobiles, the introduction of industrial robots in factories and the like, and the application of artificial intelligence (AI) to various fields are progressing, the need for infrared light receiving devices for detecting surrounding persons and the like is increasing. Is getting higher. Also, demand for nighttime surveillance cameras equipped with infrared cameras for crime prevention is increasing.

Conventionally, PbS (lead sulfide) or InGaAs (indium gallium arsenide) has been often used as a material constituting the light receiving portion of the infrared sensor as described above. However, since these materials contain harmful substances and rare metals, it has been difficult to reduce the cost of the infrared sensor. On the other hand, _{recently, Mg 2 Si 1-x Sn} x single crystal is shown to be available to the infrared sensor. However, this material is because it is difficult single _crystal, an infrared sensor using Mg _{2 Si 1-x} Sn x single crystal has not yet been realized.

Conventionally, attempts have been made to grow the Mg ₂ Si _1-x Sn _x single crystal by a vertical Bridgman method or the like. In the vertical Bridgman method, a vertical vessel loaded with a raw material melt is placed in a growth furnace having a temperature gradient, and by moving the container downward, the raw material melt is cooled and solidified in order from below to form a single crystal. It is a method of nurturing. This method is used for growing a dielectric single crystal or the like, and can grow a columnar single crystal having the same shape as a vertical container.

On the other hand, in Patent Literature 1, as a manufacturing method for obtaining a Mg ₂ Si _1-x Sn _x polycrystal as a material for a thermoelectric conversion element, BN (boron nitride) was applied to the inner wall of an alumina tube as a release agent. A production method is described in which a carbon sheet is wound and an upper part is covered with an inorganic fiber layer.

WO2011 / 115297

Conventionally, when attempting to grow a Mg ₂ Si _1-x Sn _x single crystal by the vertical Bridgman method, Mg (magnesium) is easily oxidized and easily evaporated, so the raw material is put in a quartz container and inert gas is used. Single crystals were grown by taking measures such as sealing. In addition, since Mg reacts with quartz, a mold release agent such as BN is applied to the inner surface of the container to grow. However, even in that case, the evaporated Mg reacts with the quartz, so that the quartz container could not be reused.

  On the other hand, when the method described in Patent Document 1 is to be used for the vertical Bridgman method, Mg is oxidized by the residual oxygen in the alumina tube or the carbon sheet reacts with the molten raw material. There was a problem that the outer periphery could not be used. In addition, nuclei are formed at the portions where the carbon sheet and the molten raw material have reacted, and crystals of various orientations grow from these locations, so that it has been difficult to obtain single crystals. Furthermore, in this method for growing a single crystal, it is difficult to cause convection to make the solid-liquid interface convex, so that there is a problem that bubbles remain in the crystal.

The present invention has been made in order to solve such a problem, and it is possible to reuse a crucible and to grow a Mg ₂ Si _1-x Sn _x single crystal having good crystallinity without bubbles. An object of the present invention is to provide a method and an apparatus for manufacturing a Mg ₂ Si _1-x Sn _x crystal.

In a first aspect, the method for producing a Mg ₂ Si _1-x Sn _x crystal of the present invention includes a high temperature region higher than the melting point of a raw material made of Mg, Si and Sn, and the lower portion provided below the high temperature region. in the crystal growth furnace having a low temperature region lower than the melting point of the raw material, the raw material melted in the high temperature region, performing growth of crystals by moving the molten melt material in the low temperature region Mg ₂ A method for producing a Si _1-x Sn _x crystal, wherein the raw material is loaded into a growing container made of a carbon sheet installed in a crucible, and the growing container contacts an inner surface of the growing material with Mg, A process in which a raw material composed of Si and Sn is brought into contact with a molten raw material in a molten state for a certain period of time or more so that the inner surface of the raw material is immersed in the molten raw material, and then a release material is applied to the inner surface. did It is characterized by the following.

In development of Mg ₂ Si _1-x Sn x single crystal, the crucible of the material, the structure is an important growth condition. In growing a single crystal, a quartz container is often used as a crucible, but as described above, even if the quartz container coated with a BN release agent is sealed with an inert gas, the evaporated Mg reacts with the quartz container. The crucible could not be reused. On the other hand, when a carbon sheet coated with a BN release agent is wound on the inner wall of a quartz container, Si (silicon) as a raw material reacts with carbon to generate nuclei from the portion, and crystals of various orientations grow. It was difficult to obtain a single crystal. Therefore, in the present invention, the inner surface of the growing container, which is in contact with the raw material of the carbon sheet, is brought into contact with the molten raw material in a state where the raw material of the single crystal to be grown is melted for a certain period of time or more, and the molten raw material is immersed in the inner surface in advance. By performing the above treatment, the generation of nuclei due to the reaction between Si and carbon is prevented. By inserting the growth container in which the release material such as BN is applied to the carbon sheet previously reacted with the raw material into the crucible and using the crucible, the crucible can be reused, and further, the generation of the above nuclei is prevented. It is possible to grow an Mg ₂ Si _1-x Sn _x single crystal having no bubbles and good crystallinity.

In a second aspect, the present invention provides the method for producing a Mg ₂ Si _1-x Sn _x crystal according to the _{first aspect} , wherein the crucible is made of carbon, and the crucible is charged with the growth container and the raw material. Later, a lid made of carbon is put on the upper part, and the lid is fixed using a carbon adhesive, and the crystal is grown in an inert gas atmosphere. In the invention of this aspect, the use of a carbon crucible, which is generally used in single crystal growth and has a proven track record in industry, as the crucible makes it possible to produce Mg ₂ Si _1-x Sn _x crystals at low cost. it can. In this case, since the airtightness of carbon is not high, the crystal is grown in an atmosphere of an inert gas such as Ar (argon) gas in order to prevent a reaction with oxygen. Further, a lid made of carbon is put on the upper part so that the vapor of Mg does not leak from the carbon crucible, and the lid is fixed to the crucible using a carbon adhesive.

In a third aspect, the present invention provides the method for producing a Mg ₂ Si _1-x Sn _x crystal according to the first or second aspect, wherein the high-temperature region is at least 35 ° C. higher than the melting point of the raw material. A temperature raising / lowering step comprising a high-temperature region and a second high-temperature region provided below the raw material near the melting point of the raw material, wherein the crucible is reciprocated at least once between the first high-temperature region and the second high-temperature region. And holding the crucible in the high temperature region for 1 to 2 hours including the temperature raising and lowering step, and then lowering the crucible toward the low temperature region. In the invention of this aspect, in the high-temperature region near the melting point or higher, the above-described first and second high-temperature regions are reciprocated one or more times as described above and held for a certain time to forcibly. By causing convection in the melt raw material and lowering it at a slow speed, a single crystal of higher quality without bubbles can be obtained.

According to a fourth aspect, the apparatus for manufacturing a Mg ₂ Si _1-x Sn _x crystal of the present invention includes a high temperature region higher than the melting point of a raw material composed of Mg, Si and Sn, and the lower portion provided below the high temperature region. A crystal growing furnace having a low temperature region lower than the melting point of the raw material, and a crucible inserted into the crystal growing furnace, wherein the raw material is melted in the high temperature region, and the melted raw material is melted. An apparatus for producing a Mg ₂ Si _1-x Sn _x crystal for growing a crystal by moving to a low temperature region, comprising: a growing container made of a carbon sheet installed in the crucible to load the raw material. The growing container has, on its inner surface, a molten raw material impregnated region containing Mg, Si and Sn formed by contacting a raw material composed of Mg, Si and Sn with a molten raw material in a molten state for a predetermined time or more. Yes A release material application layer formed by applying a release material is provided on the upper surface of the molten raw material impregnated region .

In a fifth aspect, the present invention provides the apparatus for producing a Mg ₂ Si _1-x Sn _x crystal according to the fourth aspect, wherein the crucible is made of carbon, and the crucible is charged with the growth container and the raw material. Having a lid made of carbon to cover the upper part of the crucible later, and having means for introducing an inert gas into the crystal growing furnace for growing the crystal in an inert gas atmosphere. I do.

As described above, according to the manufacturing method and the manufacturing apparatus of the Mg ₂ Si _1-x Sn _x crystal of the present invention, the crucible can be reused, and the Mg ₂ Si _1-x having no bubbles and excellent crystallinity can be obtained. sn _x single crystal to enable the development of the _Mg 2 _{Si 1-x} Sn x single crystal manufacturing method and a manufacturing apparatus can be obtained.

FIG. 2 is a schematic cross-sectional view illustrating an example of the configuration of an apparatus for manufacturing a Mg ₂ Si _1-x Sn _x crystal. FIG. 2 is a schematic cross-sectional view showing a configuration of a carbon crucible, a growth container, and raw materials. The figure which shows an example of the temperature distribution of the up-down direction near the carbon crucible in a carbon insulated cylinder. 3 is a photograph of a Mg ₂ Si _1-x Sn _x crystal created in Example 1. 3 is a cross-sectional photograph of a Mg ₂ Si _1-x Sn _x crystal prepared in Example 1. 5 is a photograph of a Mg ₂ Si _1-x Sn _x crystal created in Comparative Example 1. _{13 is} a cross-sectional photograph of a Mg ₂ Si _1-x Sn _x crystal created in Comparative Example 2.

Hereinafter, a method and an apparatus for manufacturing a Mg ₂ Si _1-x Sn _x crystal of the present invention will be described in detail with reference to the drawings by way of examples. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

Figure 1 is a view for explaining a method and apparatus for manufacturing a _Mg 2 _{Si 1-x} Sn x crystal according to Example _1, an example of a configuration of a manufacturing apparatus of Mg _{2 Si 1-x} Sn x crystals FIG. The present embodiment is a method for producing an Mg ₂ Si _1-x Sn _x crystal by a melt raw material descent method. That is, in a crystal growing furnace having a high temperature region higher than the melting point of a raw material composed of Mg, Si and Sn and a low temperature region lower than the melting point of the raw material provided below the high temperature region, This is a method for producing an Mg ₂ Si _1-x Sn _x crystal in which a crystal is grown by melting and moving the melted raw material to a low temperature region. In FIG. 1, a carbon crucible 5 made of carbon and a carbon heater 4 for heating are installed in a crystal growth furnace 1 made of stainless steel and having a substantially cylindrical shape. 2 are provided. Further, a carbon lid 3 is provided on the upper part of the carbon insulated cylinder 2. At the center is a crucible shaft 6 for placing and raising and lowering the carbon crucible 5. The crystal growing furnace 1 has an airtight structure, and includes a vacuum pump 7 for evacuation and a pipe 8 for introducing argon gas.

FIG. 2 is a schematic cross-sectional view showing the structure of a growth container made of a carbon crucible and a carbon sheet installed therein and raw materials. In FIG. 2, a Sn raw material 13, a Si raw material 14, and a Mg raw material 15, which are raw materials of Mg ₂ Si _1-x Sn _x crystal, are loaded in a growth container 10 made of a carbon sheet installed in a carbon crucible 5. I have. The growth vessel 10 was subjected to a process of infiltrating the melt material into the inner surface of the growth container 10 by bringing the inner surface of the growth material into contact with the melt material in a state in which the raw material was melted for a predetermined time or more. Thereafter, a release material made of BN is applied to the inner surface thereof. The opening of the carbon crucible 5 is covered with a crucible lid 11 made of carbon, and the crucible lid 11 is fixed to the carbon crucible 5 using a carbon adhesive 12.

  Next, an example of the shape of each part in the present embodiment will be described. In FIG. 1, the shape of the carbon heater 4 is a cylindrical shape having an inner diameter of 160 mm × a height of 210 mm, a crucible shaft 6 having a diameter of 30 mm is arranged at the center thereof, and a carbon crucible 5 is placed thereon. The crucible shaft 6 is connected to a moving mechanism so that it can move up and down by 200 mm. In FIG. 2, the outer shape of the carbon crucible 5 is a cylindrical shape having an outer diameter of 50 mm × a height of 80 mm, and the inside of the carbon crucible 5 has a material storage chamber having an inner diameter of 30 mm and a bottom having a conical shape with a vertex angle of 45 degrees. And it has the growth container 10 of the same shape along the inner surface.

  The thickness of the carbon sheet constituting the growing container 10 used here was 0.3 mm, and the carbon sheet was formed by molding according to the inner shape of the carbon crucible 5.

Next, a specific example of the method for manufacturing the Mg ₂ Si _1-x Sn _x crystal of the present embodiment will be described in detail. In growing a Mg ₂ Si _1-x Sn _x single crystal, high-purity magnesium having a purity of 5 N or more is used as the Mg raw material 15, high-purity silicon having a purity of 10 N or more is used as the Si raw material 14, and 5 N or more is used as the Sn raw material 13. 30 g of a raw material obtained by weighing and mixing the high-purity tin of each of the above to a required ratio is placed in a growth vessel 10 in a carbon crucible 5, and then a carbon adhesive 12 is applied to the top of the crucible lid 11 and the carbon crucible 5, The crucible lid 11 was placed and covered. The carbon crucible 5 loaded with the raw material was placed on the crucible shaft 6 and evacuated to a pressure of 1 Pa (Pascal) or less and then heated to 150 ° C. After maintaining the state for 30 minutes, the temperature was increased to 270 ° C. and further maintained for 30 minutes, thereby fixing the carbon adhesive 12 and performing vacuum sealing.

Thereafter, the raw materials were melted by the following procedure to obtain a melt raw material. First, Ar gas was introduced into the crystal growing furnace 1 and the pressure was raised to the atmospheric pressure. Then, a predetermined current was passed through the carbon heater 4 to raise the temperature of the carbon crucible 5 to 1120 ° C. The heating time was 30 minutes. At this time, the carbon crucible 5 had a center at about 1120 ° C. and a lower bottom at a position showing 1085 ° C. near the melting point. After holding for 30 minutes in this state, the bottom of the carbon crucible 5 is raised to the position of 1120 ° C. at a speed of 5 mm / min, and after holding for 30 minutes, the carbon crucible 5 is lowered to the initial position at a speed of 5 mm / min. After performing once, the crystal was grown by lowering the carbon crucible 5 at a rate of 0.5 mm / min. Incidentally, when raising the bottom of the carbon crucible 5 to the position of 1120 ° C., since the center portion of the carbon crucible 5 is in the vicinity of 1085 ° C., the first high-temperature region of 1120 ° C. The molten material by the above heating and cooling process And a second high-temperature region of 1085 ° C. FIG. 3 is a diagram showing an example of a vertical temperature distribution in the vicinity of the place where the carbon crucible 5 is placed in the carbon insulated cylinder 2.

Using the Mg ₂ Si _1-x Sn _x crystal manufacturing apparatus of the present embodiment and the Mg ₂ Si _1-x Sn _x crystal grown by the above-described manufacturing method of the present embodiment, a crystal having a wide single crystal region can be obtained. Was done. FIG. 4 shows a photograph of the Mg ₂ Si _1-x Sn _x crystal prepared in this example. In FIG. 4, since the upper surface of this crystal is glossy and convex, the raw material is repelled from the carbon sheet surface during crystal growth in this embodiment, and the solid-liquid interface is convex. It can be seen that no reaction between Si and carbon occurred. FIG. 5 shows a cross-sectional photograph of the prepared Mg ₂ Si _1-x Sn _x crystal. As can be seen from FIG. 5, the single crystal region of the crystal prepared according to the present embodiment is wide without bubbles and cracks.

(Comparative Example 1)
In order to confirm the effectiveness of the present invention, in place of the growth container 10 of Example 1, a growth container that has been molded in the same shape as the growth container 10 using the same carbon sheet as the growth container 10 of Example 1, that is, Mg ₂ Si _1-x Sn _x crystal using a growth vessel coated with a BN release agent without contacting the melt raw material for a certain period of time or more without infiltrating the melt raw material into the inner surface thereof Was trained.

In this comparative example, the same Mg ₂ Si _1-x Sn _x crystal manufacturing apparatus as in Example 1 was used. That is, the same crystal growing furnace 1, carbon heat retaining cylinder 2, carbon heater 4, etc. as in Example 1 were used. The same carbon crucible 5 and crucible lid 11 other than the growth container 10 were used.

The manufacturing method of the Mg ₂ Si _1-x Sn _x crystal of the present comparative example was also made under the exact same conditions as those of the specific example of the first embodiment. That is, the raw materials used, the loading method, the sealing method for the carbon crucible 5 and the crucible lid 11, the procedure for setting the temperature, the procedure for moving the carbon crucible 5, and the like were all the same.

The crystal grown in this comparative example was taken out and the interface state was observed. FIG. 6 shows a photograph of the Mg ₂ Si _1-x Sn _x crystal produced in this comparative example. In comparison with the crystal of Example 1 shown in FIG. 4, in this comparative example, the surface was concave as shown in FIG. 6, and it was confirmed that a reaction between Si and carbon occurred. Accordingly, in the growing container for the carbon sheet in Example 1, it is very effective to perform the treatment of infiltrating the melt material into the inner surface thereof by contacting the melt material with the melt material for a certain period of time or more. I understand.

(Comparative Example 2)
As a second comparative example for confirming the effectiveness of the present invention, the growth container 10 of Example 1 was not used, and as a growth condition, the temperature raising / lowering step in the high temperature region of the carbon crucible 5 was not performed. in was grown of _Mg 2 _{Si 1-x} Sn x crystal.

In this comparative example, the same Mg ₂ Si _1-x Sn _x crystal manufacturing apparatus as in Example 1 was used. That is, the same crystal growing furnace 1, carbon heat retaining cylinder 2, carbon heater 4, etc. as in Example 1 were used. The same carbon crucible 5 and crucible lid 11 other than the growth container 10 were used.

The manufacturing method of the Mg ₂ Si _1-x Sn _x crystal of the present comparative example is the same as that of the above-mentioned Example 1 except that the temperature raising / lowering step of raising and lowering the bottom of the carbon crucible 5 to the position of 1120 ° C. is not performed. The conditions were exactly the same as in the specific example. That is, the raw materials to be used, the loading method, the sealing method of the carbon crucible 5 and the crucible lid 11, and the procedure of temperature setting other than the above were all the same. Specifically, Ar gas was introduced into the crystal growing furnace 1 and the pressure was raised to the atmospheric pressure. Then, a predetermined current was applied to the carbon heater 4 to raise the temperature of the carbon crucible 5 to 1120 ° C. Thereafter, the temperature was maintained at 1120 ° C. for 2 hours, and then the carbon crucible 5 was lowered at a rate of 0.5 mm / min to grow crystals.

FIG. 7 shows a cross-sectional photograph of the Mg ₂ Si _1-x Sn _x crystal prepared according to this comparative example. As compared with the crystal of Example 1 shown in FIG. 5, the crystal obtained in this comparative example was a polycrystal having bubbles and cracks as shown in FIG.

As described above, it can be seen that the manufacturing method of Example 1 can provide a high-quality Mg ₂ Si _1-x Sn _x crystal having an excellent appearance compared to Comparative Examples 1 and ₂ . By providing the growth container of the present invention in a crucible, a great improvement effect can be obtained as compared with the conventional manufacturing method, and the shape of the carbon heater and the heat retaining cylinder, the selection of the shape of the crucible, and the optimal design of the temperature distribution and the like are improved. The crucible may be made of a material other than carbon, and may be made of Mg ₂ Si ₁ having a higher quality than the conventional manufacturing method without performing a temperature raising / lowering step between the first high temperature region and the second high temperature region. can be obtained _-x Sn _x crystals.

Needless to say, the present invention is not limited to the above-described embodiments, and can be changed according to the characteristics and shape of the target Mg ₂ Si _1-x Sn _x crystal. The structure, shape, material, and the like of each part of the manufacturing apparatus can be changed according to the characteristics and shape of the target Mg ₂ Si _1-x Sn _x crystal. It is desirable to optimize the growth conditions such as the temperature.

The present invention is directed to the production of thermoelectric conversion materials such as Mg ₂ Si polycrystals and Mg ₂ Si _1-x Sn _x polycrystals that can be used in power generation systems utilizing waste heat generated from factory facilities and power generation facilities. The method can also be applied.

REFERENCE SIGNS LIST 1 crystal growing furnace 2 carbon warming cylinder 3 carbon lid 4 carbon heater 5 carbon crucible 6 crucible shaft 7 vacuum pump 8 piping 10 growing vessel 11 crucible lid 12 carbon adhesive 13 Sn raw material 14 Si raw material 15 Mg raw material

Claims (5)

In a crystal growing furnace having a high temperature region higher than the melting point of a raw material made of Mg, Si and Sn and a low temperature region provided below the high temperature region and lower than the melting point of the raw material, the raw material is mixed with the high temperature region. melted, a process for the preparation of the molten melt material the low temperature region in the development of crystalline performing Mg 2 _{Si 1-x} Sn _x crystal by moving in, the material is placed in a crucible The growth container is loaded into a growth container made of a carbon sheet, and the growth container is brought into contact with a melt raw material in a state in which a raw material made of Mg, Si and Sn is melted for a predetermined time or more by contacting the inner surface with which the raw material comes into contact. A method for producing a Mg ₂ Si _1-x Sn _x crystal, characterized in that a treatment for infiltrating the melt material into the inner surface is performed, and then a release material is applied to the inner surface. The crucible is made of carbon. After the crucible is charged with the growth container and the raw material, a lid made of carbon is put on the crucible and the lid is fixed using a carbon adhesive, so that the crystal growth is not possible. method for producing a _Mg 2 _{Si 1-x} Sn x crystal according to claim 1, characterized in that in the active gas atmosphere. The high-temperature region is composed of a first high-temperature region higher than the melting point of the raw material by 35 ° C. or more and a second high-temperature region provided below the first high-temperature region near the melting point of the raw material. performs heating and cooling step of reciprocating one or more times between the second high temperature region, after the crucible was held for 1-2 hours including the temperature raising and lowering step at the high temperature region, toward the low temperature region method for producing a _Mg 2 _{Si 1-x} Sn x crystal according to claim 1 or claim 2, wherein the lowering. A crystal growth furnace having a high temperature region higher than the melting point of a raw material made of Mg, Si and Sn and a low temperature region provided below the high temperature region and lower than the melting point of the raw material, and inserted into the crystal growth furnace; Of the Mg ₂ Si _1-x Sn _x crystal, which melts the raw material in the high temperature region and moves the melted raw material to the low temperature region to grow the crystal. A production apparatus, comprising a growing container made of a carbon sheet installed in the crucible to load the raw material, wherein the growing container has an inner surface on which a raw material made of Mg, Si, and Sn is melted. A molten material impregnated region containing Mg, Si and Sn formed by being brought into contact with the molten raw material in a state for a predetermined time or more, and a release material applied by applying a release material on the upper surface of the molten material impregnated region Apparatus for producing _Mg 2 _{Si 1-x} Sn x crystals characterized by having a. The crucible is made of carbon, and has a lid made of carbon for covering the upper part of the crucible after the crucible is charged with the growth container and the raw material. The crystal is grown in an inert gas atmosphere. the apparatus for manufacturing a Mg 2 _{Si 1-x} Sn _x crystal according to claim 4, characterized in that it comprises a means for introducing inert gas into the crystal growth furnace for.