WO2017061360A1

WO2017061360A1 - Die and die pack for growing sapphire single crystals, apparatus for growing sapphire single crystals, and method for growing sapphire single crystals

Info

Publication number: WO2017061360A1
Application number: PCT/JP2016/079235
Authority: WO
Inventors: 弘倫斎藤
Original assignee: 並木精密宝石株式会社
Priority date: 2015-10-05
Filing date: 2016-10-03
Publication date: 2017-04-13

Abstract

[Problem] To provide: a sapphire single crystal which has a large diameter and exceptional crystalline quality, by rapidly determining, without the need for an extended period of time or imposing costs, the curvature R of the top surface of a die used for growing sapphire single crystals by the EFG process; and a sapphire substrate. Additionally, to provide a die and die pack for use in growing sapphire single crystals by the EFG process, and a method for growing sapphire single crystals. [Solution] Used is a die for use in growing sapphire single crystals by the EFG process, the die being characterized in that: the upper surface has a curvature R in the lengthwise direction; and the curvature R is no more than five times the width W in the lengthwise direction.

Description

Sapphire single crystal growth die and die pack, sapphire single crystal growth apparatus, sapphire single crystal growth method

The present invention relates to a sapphire single crystal growth die and die pack, a sapphire single crystal growth apparatus, and a sapphire single crystal growth method.

Conventionally, Czochralski (CZ) method, heat exchange (HEM) method, Bernoulli method, edge defined film fed growth (EFG) method and the like are known as methods for growing a single crystal. Of these, the EFG method is known as the only method for producing a flat single crystal. The EFG method is a crystal manufacturing method that has a very high utility value when manufacturing a single crystal having a predetermined crystal orientation. A sapphire single crystal grown using the EFG method requires less man-hours for processing a thin plate-like substrate. Since it can be reduced, it is used in various applications including an epitaxial growth substrate of a blue light emitting element.

Patent document 1 is known as a mass production method of a sapphire single crystal using the EFG method. In Patent Document 1, a plurality of single crystal seeds are grown by arranging and pulling up seed crystals for crystal growth in a direction perpendicular to the longitudinal direction of the raw material melt surface for growing a flat single crystal material. A method for manufacturing a sapphire single crystal and a die for growing the single crystal material are disclosed.

Patent Document 2 discloses a die in which the shape of the upper edge of the capillary in the long side direction of the silicon ribbon single crystal growth apparatus using the EFG method is recessed at the center with respect to both ends thereof. The die of Patent Document 2 is characterized by being concavely curved with a curvature of 3 W to 20 W with respect to the width dimension W in the long side direction of the upper edge of the capillary, and uses a capillary with a width dimension of 2.54 cm. It is described that a good quality ribbon crystal can be obtained by using a material having a curvature R of 250 mm when the pulling speed of the silicon ribbon crystal is 20 mm per minute and a curvature R of 150 mm when the pulling rate is 30 mm per minute. It is described that when a silicon single crystal is grown using the curved die described in Patent Document 2, the crystal defect of the grown crystal can be suppressed because the solid-liquid interface becomes a horizontal plane.

Japanese Patent No. 4465481 JP 52-156184 A

The sapphire substrate conventionally manufactured by the present applicant has been required to increase the substrate size required by the market year after year, and to increase the growth crystal. In order to cope with the increase in the diameter, a method of increasing the size of the grown crystal by changing the width in the longitudinal direction of the die has been attempted. However, the grown crystal is a crystal such as a line defect (slip) or a grain boundary (grain boundary). Many defects were generated and good large crystals could not be obtained.

In addition, the phenomenon of freezing in which the melt temporarily solidifies during crystal growth has frequently occurred. When freezing occurs, not only does the crystal quality deteriorate, but depending on the degree, the growth must be interrupted, resulting in a problem that the product yield decreases.

The present inventor has empirically obtained the knowledge that, when growing a sapphire single crystal, the use of a die having a slightly curved upper surface has the effect of suppressing the occurrence of the above crystal defects. However, even if 3W to 20W disclosed in Patent Document 2 is applied, a good large sapphire crystal could not be obtained. That is, Patent Document 2 merely shows the result that the curvatures R150 mm and 250 mm when the width W of the capillary is 2.54 cm are included in the range of 3W to 20W. Could not be applied. Therefore, for sapphire single crystals, a method for determining the optimal curvature R according to the crystal width has not been established. Conventionally, by preparing several types of dies having a changed curvature R and repeating the growth test, It is necessary to determine the optimal curvature R according to the width, which takes a long time and cost.

As described above, it is required to provide a sapphire substrate having a large diameter and excellent crystal quality to the market, and it is necessary to quickly determine an optimal curvature R without taking a long time and cost.

The present invention has been made in view of the above problems, and by quickly determining the curvature R of the die upper surface without taking a long time and cost, a sapphire single crystal and a sapphire having a large diameter and excellent crystal quality. An object is to provide a substrate. It is another object of the present invention to provide a die and a die pack applicable to sapphire single crystal growth by the EFG method, a sapphire single crystal growth apparatus, and a method for growing a sapphire single crystal.

The present inventor has found a method for quickly determining the optimum value of the curvature R of the upper surface of the die according to the grown crystal width, and when using a die and a die pack having the curvature R determined thereby, sapphire having excellent crystal quality We have found that single crystals and sapphire substrates can be mass-produced. According to the verification by the present inventor, it was found that the curvature R of the die upper surface applicable to sapphire single crystal growth is different from the numerical range shown in Patent Document 2.

(1) That is, the die according to the present invention is a die used for growing a sapphire single crystal by the EFG method, and the upper surface has a curvature R in the longitudinal direction, and the curvature R has a width W of 5 in the longitudinal direction. It is characterized by being less than double.

(2) Moreover, one embodiment of the die according to the present invention is characterized in that the main growth surface of the sapphire single crystal is a c-plane.

(3) Another embodiment of the die according to the present invention is characterized in that the curvature R is less than three times the width W.

(4) Further, another embodiment of the die according to the present invention is characterized in that the main growth surface of the sapphire single crystal is a-plane.

(5) A die pack according to the present invention is a die pack in which a plurality of the dies described in any one of (1) to (4) above are arranged in parallel and facing each other, and the number is 2 or more and 80 or less. It is characterized by being.

(6) Further, the sapphire single crystal growing apparatus according to the present invention uses the die described in any one of (1) to (4) or the die pack described in (5).

(7) The method for growing a sapphire single crystal according to the present invention is characterized by using the die according to any one of (1) to (4) or the die pack according to (5). To do.

According to the present invention, it is possible to provide a sapphire single crystal and a sapphire substrate having a large diameter and excellent crystal quality by quickly determining the curvature R of the die upper surface without taking a long time and cost. Have Furthermore, there is an effect that it is possible to provide a die and a die pack applicable to sapphire single crystal growth by the EFG method, a sapphire single crystal growth apparatus, and a sapphire single crystal growth method.

It is (a) front view and (b) side view explaining the die | dye and die pack which concern on this invention. It is a graph which shows the relationship between the width | variety W of the longitudinal direction of die | dye, and the curvature R of die upper surface. It is a schematic block diagram which shows the manufacturing apparatus of the sapphire single crystal by EFG method. (A) It is a figure which shows typically the positional relationship of the seed crystal, die | dye, and die pack in embodiment of this invention. (B) It is explanatory drawing which shows a mode that a part of seed crystal is fuse | melted in embodiment of this invention. It is a perspective view which shows typically the spraying (spreading) process of the sapphire single crystal which concerns on embodiment of this invention. It is a perspective view showing typically a plurality of sapphire single crystals obtained by the EFG method. It is a graph which shows the relationship between the width | variety W of the die longitudinal direction and the curvature R of die upper surface at the time of making the main surface of a growth crystal into c surface. It is a graph which shows the relationship between the width | variety W of the die longitudinal direction when the main surface of a growth crystal is a surface, and the curvature R of die | dye upper surface.

Hereinafter, the die and die pack according to the present invention will be described in detail with reference to FIG.

In an example of the die 101 and the die pack 102 according to the present invention, as shown in FIGS. 1A and 1B, a pair of partition plates 201 are arranged to face each other with a minute gap. The raw material melt is guided to the upper part of the die through the minute gap to form the raw material melt surface. The partition plates 201 have the same flat plate shape and are arranged in parallel so as to form a minute gap (slit 202).

FIG. 1A is a front view of a die 101 and a die pack 102 according to the present invention, and FIG. The “die” described in the present specification refers to one constituted by a pair of partition plates (201, 201). The “die pack” refers to a plurality of the dies 101 arranged in opposition so that the slits are parallel to each other.

As shown in FIGS. 1A and 1B, the upper surface of the die and the die pack according to the present invention has a curvature R with respect to the longitudinal direction of the die. The curvature R is determined by the width of the straight body portion of the crystal to be grown. The width W in the longitudinal direction of the die is designed to have the same width as the width of the straight body portion of the crystal to be grown. For example, as shown in FIG. 1A, the upper surface of the die on which crystal growth is performed preferably has an inclined surface on the upper surface and an opening having an acute angle.

According to the growth test that the present inventors actually prepared several types of dies and die packs having different curvatures R, the curvature R applicable to the sapphire single crystal growth by the EFG method is the width W in the longitudinal direction of the die. 5 times or less is preferable. By making it 5 times or less, the temperature distribution in the central part and the edge part in the longitudinal direction of the die can be reduced, so that crystal defects and growing are not related to the crystal plane of the main growth surface of the sapphire single crystal. It is possible to suppress the occurrence of freezing in the sapphire, and a sapphire single crystal having excellent crystal quality can be manufactured. In addition, the die can be easily designed.

Further, according to the verification by the inventor's growth test, when obtaining the optimum value of the curvature R with respect to the width W for each growth principal surface, in addition to setting it to be not more than 5 times the width W, a mathematical function R = It is preferable to apply eW ² + fW. A technique for obtaining the optimum value of the curvature R by applying a quadratic function is a technique found by the present inventor based on an example described later. FIG. 2 is a graph showing the relationship between the longitudinal width W of the die and the curvature R of the upper surface of the die. By applying a quadratic function R = eW ² + fW, the curvature R can be obtained for any crystal width. It is possible to easily determine the optimum value of.

Here, e is preferably set to a value of 0.001 or more and 0.2 or less regardless of the main growth surface of the grown crystal. In addition to e, f is preferably 0.001 or more and 3 or less. By setting e and f within the above numerical range, it is possible to suppress the occurrence of crystal defects and freezes regardless of the growth main surface of the grown crystal, and a sapphire single crystal having excellent crystal quality can be manufactured.

According to the verification by the inventor's growth test, e and f may be selected in an optimal numerical range depending on the growth main surface of the grown crystal. For example, when the growth principal surface is the c-plane, e is preferably 0.001 or more and 0.2 or less, and f is preferably 0.001 or more and 3 or less, and e is 0.001 or more and 0.05 or less, and , F is more preferably 0.001 or more and 3 or less. In addition to the conditions of e and f, it is preferable that R / W is set to have a value of less than 3. That is, when the growth main surface is a c-plane, the curvature R is preferably less than three times the width W in the longitudinal direction of the die. Since the numerical ranges are set for e and f, it is possible to ensure a slight degree of design freedom even when the width W is the same and the thickness of the grown crystal and the number of dies are different.

Moreover, when the main surface is a-plane, e is preferably 0.001 or more and 0.1 or less, and more preferably e is 0.005 or more and 0.05 or less. In addition to e, the value of f is preferably 0.5 or more and 2.5 or less.

Further, the curvature R obtained by the formula R = eW ² + fW can be changed as necessary within a range of ± 25% at maximum, preferably ± 10%, more preferably ± 5%, Die processing difficulty can be reduced. Therefore, the die processing cost can be reduced.

In the die and die pack of the present invention, the width W in the longitudinal direction corresponds to the width of the grown crystal, and the width is desirably 20 mm or more and 300 mm or less. When the width W is as small as less than 20 mm, the effect itself of providing the curvature R in the longitudinal direction of the die is small, which is not preferable. On the other hand, if it exceeds 300 mm, it is difficult to obtain the optimum value of the curvature R using the above-described mathematical formula, which is not preferable. By setting it to 20 mm or more and 300 mm or less, it is possible to grow a large sapphire single crystal excellent in crystal quality and corresponding to a large-diameter sapphire substrate up to 300 mm or less.

As shown in FIG. 1A, the thickness t of the die 101 constituted by a pair of partition plates corresponds to the thickness of the grown crystal. The die of the present invention desirably has a thickness t of 1 mm or more and 10 mm or less. By setting the thickness t to 1 mm or more, the strength and self-supporting property of the grown sapphire single crystal itself can be ensured. Furthermore, even when processing into a sapphire substrate, a sufficient processing allowance can be ensured. Moreover, since it will become difficult to obtain the sapphire single crystal excellent in crystal quality when thickness t exceeds 10 mm, it is preferable to set it as 10 mm or less.

In addition, an example of the die pack 102 of the present invention is one in which a plurality of sets of the dies are arranged so that the slits are parallel to each other. In the present invention, the number is preferably from 2 to 80, more preferably from 2 to 50. When the die pack of the present invention is used, a plurality of sapphire single crystals can be grown from a common seed crystal, so that mass productivity can be improved. However, the number is limited by the grown crystal width and crystal thickness. When the number of grown crystals exceeds 80, it is not preferable because it becomes difficult to adjust the temperature balance in the number direction.

The material of the die and die pack is preferably refractory metal molybdenum or molybdenum alloy suitable for use at a high temperature exceeding 2000 ° C. during sapphire single crystal growth.

The die and the die pack are produced according to the grown crystal width and thickness, and the number of grown crystals, and are placed in a crucible.

Hereinafter, a method for growing a sapphire single crystal in the EFG method using the die and the die pack according to the present invention will be described in detail with reference to FIGS. Here, a case where a plurality of sapphire single crystals are grown using a die pack will be described. However, a case where a single sapphire single crystal is grown using a die can also be grown similarly.

As shown in FIG. 3, the sapphire single crystal manufacturing apparatus 3 includes a growth container 4 for growing a sapphire single crystal and a pulling container 5 for pulling up the grown sapphire single crystal. Crystal 20 is grown.
The growth container 4 includes a crucible 6, a crucible driving unit 7, a heater 8, an electrode 9, a die pack 102, and a heat insulating material 10. The crucible 6 is made of molybdenum or an alloy of molybdenum and melts the aluminum oxide raw material. The crucible drive unit 7 rotates the crucible 6 with the vertical direction as an axis. The heater 8 heats the crucible 6. The electrode 9 energizes the heater 8.

The die pack 102 is installed in the crucible 6 and determines the liquid surface shape of an aluminum oxide melt (hereinafter simply referred to as “melt” if necessary) when pulling up the sapphire single crystal. The heat insulating material 10 surrounds the crucible 6, the heater 8, and the die pack 102.

Furthermore, the growth container 4 includes an atmospheric gas inlet 11 and an exhaust 12. The atmosphere gas inlet 11 is an inlet for introducing, for example, argon gas into the growth vessel 4 as the atmosphere gas, and prevents oxidation of the crucible 6, the heater 8, and the die pack 102. On the other hand, the exhaust port 12 is provided for exhausting the inside of the growth vessel 4.

The pulling container 5 includes a shaft 13, a shaft driving unit 14, a gate valve 15, and a substrate inlet / outlet 16, and pulls up a plurality of sapphire single crystals 20 grown from the seed crystal 21. The shaft 13 holds the seed crystal 21. Further, the shaft driving unit 14 moves the shaft 13 up and down toward the crucible 6 and rotates the shaft 13 around the lifting direction. The gate valve 15 partitions the growth container 4 and the pulling container 5. The substrate entrance / exit 16 takes in and out the seed crystal 21.

The manufacturing apparatus 3 also has a control unit (not shown), and the rotation of the crucible drive unit 7 and the shaft drive unit 14 is controlled by this control unit.

Next, a method for manufacturing the sapphire single crystal 20 using the manufacturing apparatus 3 will be described with reference to FIGS. First, a predetermined amount of granulated aluminum oxide raw material powder (99.99% aluminum oxide), which is a raw material of sapphire single crystal, is charged into a crucible 6 in which a die pack 102 is housed. The aluminum oxide raw material powder may contain compounds and elements other than aluminum oxide depending on the purity or composition of the sapphire single crystal to be produced.

Subsequently, in order not to oxidize the crucible 6, the heater 8, or the die pack 102, the inside of the growth vessel 4 is replaced with argon gas, and the oxygen concentration is set to a predetermined value or less.
Next, the crucible 6 is heated to a predetermined temperature by the heater 8 to melt the aluminum oxide raw material powder. Since the melting point of aluminum oxide is about 2050 ° C. to 2072 ° C., the heating temperature of the crucible 6 is set to a temperature higher than the melting point (for example, 2100 ° C.). After a while after heating, the raw material powder melts and an aluminum oxide melt 17 is prepared. As shown in FIG. 4A, a part of the melt ascends through the slit 202 of the die due to capillary action and reaches the surface of the die pack 102, and the melt pool 18 is formed above the slit.

Next, as shown in FIG. 4B, the seed crystal 21 is lowered while holding the seed crystal 21 at an angle perpendicular to the longitudinal direction of the melt reservoir 18 above the slit, and the seed crystal 21 is melted in the melt reservoir 18. Touch the liquid surface. The seed crystal 21 is previously introduced into the pulling container 5 from the substrate entrance 16.

The shape of the seed crystal 21 shown in FIGS. 4A and 4B is an example. By arranging the plane direction of the seed crystal 21 and the longitudinal direction of the die pack 102 so as to be orthogonal to each other at an angle of 90 °, it is possible to simultaneously grow a plurality of sapphire single crystals from one seed crystal. It becomes. Therefore, the plane direction of the grown sapphire single crystal 20 is also orthogonal to the plane direction of the seed crystal 21 at an angle of 90 °.
Next, the neck portion 22 is formed as shown in FIG. Specifically, first, a thin neck portion 22 is produced (necked) while the substrate holder is raised at high speed by the shaft 13. Hereinafter, this process is referred to as a necking process.

The neck portion 22 is a crystal portion having a diameter as thin as the thickness of the seed crystal 21 or the width of the melt pool 18 and is formed to reduce or eliminate crystal defects. The length of the neck portion 22 is formed up to about three times its diameter. When the crystal is grown to this extent, even if a crystal defect occurs in the neck portion 22, the defect is prevented from being formed up to the sapphire single crystal 20. Therefore, by passing through the necking step, it is possible to manufacture a flat sapphire single crystal 20 in which crystal defects are reduced or eliminated.

After passing through the necking step, the heater 8 is controlled to lower the temperature of the crucible 6, and the substrate holder is set at a predetermined speed, with the seed crystal 21 as the center, as shown in FIG. The crystal 20 is grown so as to be widened in the longitudinal direction of the die (spraying process). FIG. 5 is a schematic view showing a state in which the width of the sapphire single crystal 20 is widened by a spraying process.

When the sapphire single crystal 20 is expanded to the full width of the die (full spread), growth of the straight body portion 23 having a crystal width defined by the width W in the longitudinal direction of the die is started (straight body process). In the straight body process, a plurality of sapphire single crystals 20 having a straight body portion defined by side surfaces that are substantially parallel to and opposed to each other are manufactured. The length of the straight body is not particularly limited, but is preferably 2 inches or more (50.8 mm or more). A plurality of sapphire single crystals 20 as shown in FIG. 6 are obtained through the above-described necking process, spraying process, and straight body process.

Thereafter, the plurality of sapphire single crystals 20 obtained are allowed to cool, the gate valve 15 is opened, moved to the pulling container 5 side, and taken out from the substrate inlet / outlet 16.

By using the manufacturing apparatus 3 and the die pack 102 as described above, a plurality of sapphire single crystals 20 can be manufactured from the common seed crystal 21. Note that the crystal plane of the main surface of the sapphire single crystal 20 can be arbitrarily changed by arbitrarily setting the crystal plane of the seed crystal 21. The main surface of the sapphire single crystal 20 is not limited to the a-plane, and can be set to a desired crystal plane such as a c-plane, r-plane, or m-plane.

Using the die pack 102 shown in FIG. 1 and the sapphire single crystal manufacturing apparatus 3 shown in FIG. 3, a plurality of sapphire single crystals 20 having the c-plane as the main surface were manufactured by the method described above. The curvature R (mm) of the die upper surface and the width W (mm) in the longitudinal direction of the die were changed as parameters of the die pack 102 as shown in Table 1, and the sapphire single crystals of Examples 1 to 5 and Comparative Examples 1 and 2 20 was obtained. The die thickness t in Examples 2 to 4 where the width W is 105 mm and Comparative Example 1 are the same. Further, the number of breeding in Examples 3 and 4 and Comparative Example 1 is the same, and the number of breeding is different from that in Examples 1 and 2. In addition, the thickness t and the number of growth of the dies in Example 5 and Comparative Example 2 in which the width W is 155 mm are the same.

When the crystallinity of the obtained sapphire single crystal 20 was evaluated, in Examples 1 to 5, there were no crystal defects such as line defects and crystal grain boundaries. There was a crystal grain boundary and the crystallinity was not good.

FIG. 7 is a graph showing the relationship between the width W in the die longitudinal direction and the curvature R of the die upper surface when the main surface of the grown crystal is the c-plane. In the graph, Examples 1 to 5 are plotted with ◆, and Comparative Examples 1 and 2 are plotted with ×. The curve shown in the graph is an approximate curve obtained by approximating the data of Examples 1 to 5 by the least square method, and is a quadratic curve indicating the relationship of the formula R = eW ² + fW.

As shown in FIG. 7, Examples 1 to 5 in which good single crystals were obtained satisfy the relational expression R = eW ² + fW described above, but Comparative Examples 1 and 2 are slightly different from the relational expression. With the straight line R = 3W shown in the graph as a boundary, R was less than 3W, and the product was non-defective when R was 3W or more. Further, in the range where R is less than 0.05 W, it is difficult to satisfy the lower limit values of the coefficients e and f of the formula R = eW ² + fW described above.

Therefore, in the method for growing a sapphire single crystal using the sapphire single crystal growth apparatus in the EFG method of the present invention, when the main growth surface of the sapphire single crystal is a c-plane, the curvature R of the die upper surface is set in the longitudinal direction of the die. It was found that a good sapphire single crystal can be grown by setting it to less than 3 times the width W. Furthermore, it has been found that it is more preferable that R satisfies the formula R = eW ² + fW while satisfying less than 3W.

Next, using the die pack 102 shown in FIG. 1 and the sapphire single crystal manufacturing apparatus 3 shown in FIG. 3, the sapphire single crystal 20 having the a-plane as the main surface was manufactured by the method described above. The curvature R (mm) of the die upper surface and the width W (mm) in the longitudinal direction of the die are changed as parameters of the die pack 102 as shown in Table 1, and a plurality of sapphires of Examples 6 to 9 and Comparative Examples 3 and 4 are used. Single crystal 20 was obtained. It should be noted that the thicknesses t and the number of grown dies are the same in Examples 7 and 8 where the width W is 138 mm and Comparative Example 3. Further, the die thickness t and the number of growths in Example 9 and Comparative Example 4 in which the width W is 150 mm are the same.

When the crystallinity of the obtained sapphire single crystal 20 was evaluated, in Examples 6 to 9, there were no crystal parts such as line defects and crystal grain boundaries, but in Comparative Examples 3 and 4, the line defects and There was a crystal grain boundary and the crystallinity was not good.

FIG. 8 is a graph showing the relationship between the width W in the die longitudinal direction and the curvature R of the die upper surface when the principal surface of the grown crystal is the a-plane. In the graph, Examples 6 to 9 are plotted with ◆, and Comparative Examples 3 and 4 are plotted with ×. Similar to FIG. 7, the curve shown in the graph of FIG. 8 is an approximate curve obtained by approximating the data of Examples 6 to 9 by the method of least squares, and is a quadratic curve indicating the relationship of the formula R = eW ² + fW. .

As shown in FIG. 8, Examples 6 to 9 in which good single crystals were obtained satisfy the relational expression R = eW ² + fW described above, but Comparative Examples 3 and 4 are slightly different from the relational expression. When the straight line R = 5W shown in the graph was used as a boundary, R was 5W or less, and the product was non-defective. Further, in the range where R is less than 0.05 W, it is difficult to satisfy the lower limit values of the coefficients e and f of the formula R = eW ² + fW described above.

Therefore, in the method for growing a sapphire single crystal using the sapphire single crystal growth apparatus in the EFG method of the present invention, when the main growth surface of the sapphire single crystal is a-plane, the curvature R of the die upper surface is set in the longitudinal direction of the die. It turned out that a favorable sapphire single crystal can be grown by setting it as 5 times or less of the width W. Furthermore, it has been found that it is more preferable that R satisfies 5W or less and satisfies the formula R = eW ² + fW.

In FIG. 7, in the region where W is greater than about 220 mm, R = eW ² + fW is such that R is 3W or more. In this region, if R is 5 W or less as shown in FIG. 8, it is expected that a good single crystal can be grown by satisfying the relational expression R = eW ² + fW. As shown in FIG. 7, since a line defect or a crystal grain boundary occurs with R = 3W as a boundary, it is preferable that R is less than 3W with a margin. Similarly, in the case of the a-plane shown in FIG. 8, it is preferable that R is 5 W or less.

The sapphire single crystal grown using the die and the die pack of the present invention has no crystal defects such as a line defect (slip) and a grain boundary (grain boundary) in the straight body portion, and is excellent in crystal quality. “The straight body portion has no crystal defects” means that the crystal defects as described above do not exist in the region used for substrate processing in the straight body portion of the grown crystal. Specifically, since there is no crystal defect in a region within 95% of the width of the grown crystal, the product yield can be improved. Further, the shape of the lower end surface of the straight body portion of the grown crystal is formed to be concave with respect to the pulling direction. This is because the upper surface of the die of the present invention has a curvature in the longitudinal direction. By polishing the sapphire single crystal thus obtained, a sapphire substrate having excellent crystal quality can be provided.

DESCRIPTION OF SYMBOLS 101 Die 102 Die pack 201 Partition plate 202 Slit 3 Sapphire single crystal manufacturing apparatus 4 Growth vessel 5 Pulling vessel 6 Crucible 7 Crucible drive unit 8 Heater 9 Electrode 10 Heat insulating material 11 Atmospheric gas introduction port 12 Exhaust port 13 Shaft 14 Shaft drive unit 15 Gate valve 16 Substrate inlet / outlet 17 Aluminum oxide melt 18 Aluminum oxide melt pool 20 Multiple sapphire single crystals 21 Seed crystal 22 Neck portion 23 Straight barrel portion R Die upper surface curvature W Die longitudinal width t Die thickness

Claims

A die used for growing a sapphire single crystal by an EFG method, wherein an upper surface has a curvature R in a longitudinal direction, and the curvature R is not more than 5 times a width W in a longitudinal direction.
The die according to claim 1, wherein the main growth surface of the sapphire single crystal is a c-plane.
The die according to claim 2, wherein the curvature R is less than three times the width W.
The die according to claim 1, wherein a main growth surface of the sapphire single crystal is an a-plane.
5. A die pack in which a plurality of sets of the dies according to claim 1 are arranged to face each other in parallel, and the number thereof is 2 or more and 80 or less.
An apparatus for growing a sapphire single crystal in the EFG method, the apparatus for growing a sapphire single crystal using the die according to any one of claims 1 to 4 or the die pack according to claim 5.
A method for growing a sapphire single crystal in an EFG method, wherein the die according to any one of claims 1 to 4 or the die pack according to claim 5 is used.