JP6014838B1 - Multiple sapphire single crystals and method for producing the same - Google Patents

Abstract

Provided are a plurality of sapphire single crystals excellent in mass productivity and a method for producing the same by controlling variations in spraying speed between sapphire single crystals in multi-growth of sapphire single crystals. By optimizing the balance between the temperature gradient in the longitudinal direction of the die and the temperature gradient in the direction in which the dies are arranged, the dispersion of the spraying speed is controlled and the transition start point to the straight body portion is determined as a sapphire single crystal. Is set to a value within a predetermined range according to the width of the straight body portion. [Selection] Figure 2

Description

  The present invention relates to a plurality of sapphire single crystals and a method for producing the same.

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 extremely high utility value when manufacturing a single crystal having a predetermined crystal orientation, and a sapphire single crystal grown by using the EFG method can reduce the man-hour for substrate processing. Since it has an advantage that it can be used, 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 seed crystal for crystal growth is arranged and pulled up in a direction orthogonal to the longitudinal direction of the raw material melt surface for growing a flat plate-shaped single crystal, thereby pulling a plurality of single crystals from one seed crystal. A method for producing a sapphire single crystal for growing crystals is described. In the manufacturing method of Patent Document 1, the probability of crystal defects can be reduced by reducing the contact area between the seed crystal and the molten liquid surface of the raw material, thereby improving the yield of the sapphire single crystal to be manufactured. It becomes possible.

Patent Document 2 discloses a sapphire single crystal having a width of 25 cm or more and a thickness of 0.5 cm or more and having a neck and a main body. A sapphire single crystal characterized in that the distance ΔT between the transition points projected in the length direction of the sapphire single crystal is 4.0 cm or less.

Japanese Patent No. 4465481 Japanese Patent No. 5091662

  As described in Patent Document 1, in so-called multi-growth in which a plurality of single crystals are pulled up from a single seed crystal, usually, after forming a neck portion, the temperature of the raw material melt is lowered to increase the length of the die. The crystal growth of the straight body portion is started through a spreading process of expanding the width of the crystal until reaching the length.

However, in the multi-growth of sapphire single crystals, dispersion of the spraying speed between the respective sapphire single crystals has been a problem. In other words, if there is a sapphire single crystal that moves extremely slowly to the straight body part, the spraying part will be extended in the length direction of the single crystal, so the area of the straight body part will be reduced and processing to the sapphire substrate There was a problem that the number of sheets decreased. In addition, if the crystal growth progresses without the spraying speed being extremely slow and the straight body portion not fully extending to the predetermined die width (length in the longitudinal direction of the die), it can be processed into a sapphire substrate of the specified size. Disappear. Furthermore, such a sapphire single crystal has a problem that the crystal quality is deteriorated, for example, crystal defects are likely to occur.

Patent Document 2 discloses a technical content for adjusting the temperature gradient along the die so that the ΔT is 4.0 cm or less. However, the sapphire single crystal has a large size of 25 cm or more in width. It is limited to. Accordingly, there is a problem that it cannot be applied to multi-growth aimed at mass-producing crystals having various substrate sizes (especially less than 10 inches) required by the market.

The present invention has been made in view of the above problems, and by controlling the dispersion of the spraying speed between each sapphire single crystal that has occurred in multi-growth, the mass productivity of sapphire single crystals in various sizes and The object is to improve the crystal quality. Furthermore, it aims at improving the mass productivity of a sapphire substrate.

In the multi-growth of sapphire single crystals, the present inventors have optimized the balance between the temperature gradient in the longitudinal direction of the die and the temperature gradient in the direction in which the dies are arranged in the direction perpendicular to the longitudinal direction of the die. It has been found that the above problem can be solved by controlling the dispersion of the ding speed and setting the starting point of the transition to the straight body part to a value within a predetermined range according to the width of the straight body part of the sapphire single crystal. Completed the invention.

That is, a plurality of sapphire single crystals according to the present invention are connected to a common seed crystal at least through a spraying portion and are substantially parallel to each other, and have a straight body portion that is defined by side surfaces that are substantially parallel to and opposed to each other. A plurality of sapphire single crystals having a straight cylindrical portion having the same width and a flat plate shape , wherein the number n of the plurality of sapphire single crystals is n ≧ 2, and among the plurality of sapphire single crystals, spray migration earliest initiated initial migration start point a to the point from loading portion to the straight body portion, the slowest initiated point as the last transfer start point B, the in pulling direction of the plurality of sapphire single crystal When the distance between A and B is ΔTm and the width of the straight body portion of the sapphire single crystal is W, the ΔTm value is 0.3 W or less.

In one embodiment of the plurality of sapphire single crystals according to the present invention, the ΔTm value is preferably 0.2 W or less.

Further, in another embodiment of the plurality of sapphire single crystals according to the present invention, it is preferable that the variation in the thickness t between the sapphire single crystals is 0.10 t or less.

In another embodiment of the plurality of sapphire single crystals according to the present invention, the variation in the thickness t of each sapphire single crystal is preferably 0.10 t or less over the entire surface of the straight body portion of each sapphire single crystal. .

In another embodiment of the plurality of sapphire single crystals according to the present invention, the width W of the straight body portion of the sapphire single crystal is preferably 1.0 cm or more and 26.0 cm or less.

Further, in another embodiment of the plurality of sapphire single crystals according to the present invention, the width W of the straight body portion of the sapphire single crystal is 1.0 cm or more and 26.0 cm or less, and the thickness t of each sapphire single crystal is It is preferable that it is 0.05 cm or more and 1.5 cm or less.

In another embodiment of the plurality of sapphire single crystals according to the present invention, the width W is preferably 5.0 cm to 22.0 cm.

Also, the method for producing a plurality of sapphire single crystals according to the present invention includes housing a plurality of dies having slits in a crucible, charging an aluminum oxide raw material into the crucible and heating, and melting the aluminum oxide raw material in the crucible. A common seed crystal is prepared by preparing an aluminum oxide melt, forming an aluminum oxide melt pool at the top of the slit through the slit, bringing the seed crystal into contact with the aluminum oxide melt above the slit, and pulling up the seed crystal. A plurality of straight cylinder portions that are connected to each other at least through the spraying portions and defined by side surfaces that are substantially parallel to and opposed to each other, and the widths of the straight cylinder portions are equal to each other in a flat plate shape . A method of manufacturing a sapphire single crystal, wherein the number n of the plurality of sapphire single crystals is n ≧ 2, and among the plurality of sapphire single crystals, Transition from the spray loading portion to the straight body portion and earliest initiated initial migration start point A to point slowest initiated last transfer start point B to point, in the pulling direction of the plurality of sapphire single crystal The ΔTm value is 0.3 W or less, where ΔTm is the distance between the A and B, and W is the width of the straight body portion of the sapphire single crystal.

In one embodiment of the method for producing a plurality of sapphire single crystals according to the present invention, the ΔTm value is preferably 0.2 W or less.

In another embodiment of the method for producing a plurality of sapphire single crystals according to the present invention, the variation in the thickness t between the sapphire single crystals is preferably 0.10 t or less.

In another embodiment of the method for producing a plurality of sapphire single crystals according to the present invention, the variation of the thickness t of each sapphire single crystal is 0.10 t or less over the entire straight body portion of each sapphire single crystal. It is preferable.

In another embodiment of the method for producing a plurality of sapphire single crystals according to the present invention, the width W of the straight body portion of the sapphire single crystal is preferably 1.0 cm or more and 26.0 cm or less.

In another embodiment of the method for producing a plurality of sapphire single crystals according to the present invention, the width W of the straight body portion of the sapphire single crystal is 1.0 cm or more and 26.0 cm or less, and the thickness of each sapphire single crystal. It is preferable that t is 0.05 cm or more and 1.5 cm or less.

In another embodiment of the plurality of sapphire single crystals according to the present invention, the width W is preferably 5.0 cm or more and 22.0 cm or less.

According to the present invention, in the multi-growth of sapphire single crystals, by controlling the dispersion of the spraying speed between the sapphire single crystals, the transition start point to the straight body portion is set to the width of the straight body portion of the sapphire single crystal. Accordingly, it is possible to set within a predetermined range, and it is possible to improve the mass productivity and crystal quality of the sapphire single crystal. Furthermore, there is an effect that the mass productivity of the sapphire substrate can be improved.

It is a perspective view explaining a plurality of sapphire single crystals concerning the present invention. It is a perspective view explaining an example of ΔTm according to an embodiment of the present invention. It is a schematic block diagram which shows the manufacturing apparatus of the sapphire single crystal by EFG method. (a) It is a top view which shows typically an example of the die | dye which concerns on embodiment of this invention. (b) It is a front view of the figure (a). (c) It is a side view of the figure (a). (a) It is explanatory drawing which shows an example of the seed crystal which concerns on embodiment of this invention. (b) It is explanatory drawing which shows the other example of the seed crystal which concerns on embodiment of this invention. (c) It is explanatory drawing which shows the further another example of the seed crystal which concerns on embodiment of this invention. It is a perspective view which shows typically the positional relationship of the seed crystal and partition plate in embodiment of this invention. (a) It is a front view which shows typically the positional relationship of the seed crystal and partition plate 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 a mode that the neck part in embodiment of this invention grows. (a) In the seed crystal which concerns on embodiment of this invention, a lower side is explanatory drawing which shows a comb-tooth shaped seed crystal. (b) In the seed crystal which concerns on embodiment of this invention, a lower side is explanatory drawing which shows a saw-shaped seed crystal. It is a perspective view which shows typically the spraying process of the sapphire single crystal which concerns on embodiment of this invention. It is a perspective view which shows typically the some sapphire single crystal obtained by EFG method. It is a perspective view which shows typically the positional relationship of a seed crystal and a partition plate in the example of a change of embodiment of this invention.

  Hereinafter, with reference to FIG.1 and FIG.2, the several sapphire single crystal which concerns on this invention is demonstrated in detail.

As shown in FIG. 1, the plurality of sapphire single crystals 1 according to the present invention are connected to a common seed crystal through at least a spraying portion 3 so as to be substantially parallel to each other , and are defined by side surfaces that are substantially parallel to and opposed to each other. It has a straight body portion 4 that is, the width of the straight body portion 4 is equally flat shape. The plurality of sapphire single crystals 1 are grown from a common seed crystal 2 in the form shown in FIG. 1, and the number n of sapphire single crystals is two or more.

When a sapphire single crystal is grown by the EFG method, the spraying portion 3 is usually formed after the neck portion 5 is formed. As will be described later, the neck portion 5 is a crystal portion having a thin diameter about the thickness of the seed crystal or the melt pool, and is formed in order to reduce or remove crystal defects at an early stage of crystal growth. Is. The spraying portion 3 is formed to increase the width of the crystal until the length of the die in the longitudinal direction is reached and to grow a straight body portion of the sapphire single crystal.

When attention is paid to each sapphire single crystal, there is a slight shift of the transition start point to the straight body portion due to variations in the spraying speed. Here, as shown in FIG. 2, among the plurality of sapphire single crystals 1, the point at which the transition from the spraying portion 3 to the straight body portion 4 is started earliest is the first transition start point A, and the latest start is the latest. ΔTm is the distance between AB in the pulling direction of the sapphire single crystal.

In the plurality of sapphire single crystals according to the present invention, when the width of the straight body portion of the sapphire single crystal is W, ΔTm is suppressed to a value corresponding to W, specifically 0.3 W or less. Here, the width W of the straight body portion of the sapphire single crystal is defined by the length in the longitudinal direction of the die. That is, ideally, the width W of the straight body portion of the sapphire single crystal is equal to the length in the longitudinal direction of the die. As W increases, it takes a longer time to shift to the straight body portion, and thus the dispersion of the spraying speed tends to increase, and ΔTm becomes a large value.

If ΔTm exceeds 0.3 W, the balance between the temperature gradient in the longitudinal direction of the die and the temperature gradient in the direction in which the dies are arranged cannot be said to be good, and the dispersion of the spraying speed increases. That is, the crystal quality and mass productivity of the sapphire single crystal are reduced. By setting the ΔTm value to 0.3 W or less, it is possible to produce a sapphire single crystal with good crystal quality and further improve mass productivity.

Further, by suppressing ΔTm to 0.2 W or less, more preferably 0.1 W or less, the mass productivity of the sapphire single crystal can be further improved, and the crystal quality can be further improved.

  As described above, the value of ΔTm is related to the temperature gradient in the longitudinal direction of the die and the temperature gradient in the direction in which the dies are arranged. Therefore, as ΔTm increases, the balance of the temperature gradient in the biaxial direction of the die increases. Is not good. Therefore, although ΔTm is ideally 0, in practice, a slight temperature gradient in the biaxial direction always occurs.

  Further, in the plurality of sapphire single crystals according to the present invention, variation in the thickness t between the sapphire single crystals is suppressed to 0.10 t or less by suppressing ΔTm to 0.3 W or less. Here, the thickness t of each sapphire single crystal is defined by the thickness of the die. That is, ideally, the thickness t of each sapphire single crystal = the thickness of the die. In practice, however, the thickness t between the sapphire single crystals varies slightly.

The variation in the thickness t between the sapphire single crystals means the variation in the thickness t of each sapphire single crystal among the sapphire single crystals grown along the direction in which the dies are arranged. By setting the variation in the thickness t between the sapphire single crystals to 0.10 t or less, the mass productivity of the sapphire single crystal can be further improved.

Further, the variation of the thickness t of each sapphire single crystal is suppressed to 0.10 t or less over the entire straight body portion of each sapphire single crystal by suppressing ΔTm to 0.3 W or less. Therefore, the mass productivity of the sapphire single crystal can be further improved.

The variation in the thickness t between the sapphire single crystals described above and the variation in the thickness t of each sapphire single crystal are ideally zero, but slight thickness variations always occur.

Further, the plurality of sapphire single crystals according to the present invention have a width W of a straight body portion of the sapphire single crystal of 1.0 cm or more and 26.0 cm or less, and various sizes from less than 0.5 inch to about 10 inches. The mass productivity of the single sapphire crystal can be improved. By setting the width W to 1.0 cm or more, it is possible to manufacture an extremely small sapphire substrate and improve its mass productivity. Further, by setting the width W to 26.0 cm or less, a large-sized 10-inch sapphire substrate can be manufactured, and its mass productivity can be improved.

In the plurality of sapphire single crystals according to the present invention, the width W of the straight body portion of the sapphire single crystal is 1.0 cm or more and 26.0 cm or less, and the thickness t of each sapphire single crystal is 0.05 cm or more and 1. It becomes 5 cm or less, and it becomes possible to improve the mass productivity of sapphire single crystals in various sizes from less than 0.5 inch to about 10 inches. By setting the thickness t to 0.05 cm 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 1.5 cm, it is preferable to set it as 1.5 cm or less.

In the plurality of sapphire single crystals according to the present invention, the width W of the straight body portion of the sapphire single crystal is particularly preferably 5.0 or more and 22.0 cm or less. By making W within the above-mentioned numerical range, mass production of sapphire single crystals in various sizes from about 2 inches (50.8 cm) to about 8 inches (203.2 cm), which is particularly versatile as a sapphire substrate, is achieved. Can be improved. The width W is set to 5.0 or more and 22.0 cm or less in consideration of processing cost for a 2 to 8 inch substrate.

According to the present invention, the mass productivity of a sapphire single crystal can be improved, and further the mass productivity of a sapphire substrate can be improved.

Hereinafter, the manufacturing method of the several sapphire single crystal which concerns on this invention is demonstrated in detail, referring FIGS. 3-12. Hereinafter, the “plurality of sapphire single crystals” are simply referred to as “sapphire single crystals” as necessary.

As shown in FIG. 3, the sapphire single crystal manufacturing apparatus 6 includes a growth container 7 for growing a sapphire single crystal and a pulling container 8 for pulling up the grown sapphire single crystal. Grow 1

The growth container 7 includes a crucible 9, a crucible drive unit 10, a heater 11, an electrode 12, a die 13, and a heat insulating material 14. The crucible 9 is made of molybdenum and melts the aluminum oxide raw material. The crucible drive unit 10 rotates the crucible 9 with the vertical direction as an axis. The heater 11 heats the crucible 9. The electrode 12 energizes the heater 11. The die 13 is installed in the crucible 9 and determines the liquid surface shape of the aluminum oxide melt (hereinafter simply referred to as “melt” as necessary) when pulling up the sapphire single crystal. The heat insulating material 14 surrounds the crucible 9, the heater 11 and the die 13.

  Further, the growth container 7 includes an atmospheric gas introduction port 15 and an exhaust port 16. The atmosphere gas inlet 15 is an inlet for introducing, for example, argon gas into the growth vessel 7 as the atmosphere gas, and prevents oxidation of the crucible 9, the heater 11, and the die 13. On the other hand, the exhaust port 16 is provided for exhausting the inside of the growth vessel 7.

The pulling container 8 includes a shaft 17, a shaft driving unit 18, a gate valve 19, and a substrate inlet / outlet 20, and pulls up a plurality of sapphire single crystals 1 grown and grown from the seed crystal 2. The shaft 17 holds the seed crystal 2. Further, the shaft driving unit 18 moves the shaft 17 up and down toward the crucible 9 and rotates the shaft 17 around the lifting direction. The gate valve 19 partitions the growth container 7 and the pulling container 8. The substrate entrance / exit 20 takes in and out the seed crystal 2.

The manufacturing apparatus 6 also has a control unit (not shown), and the rotation of the crucible driving unit 10 and the shaft driving unit 18 is controlled by this control unit.

Next, the die 13 will be described. The die 13 is made of molybdenum and has a number of partition plates 21 as shown in FIG. In FIG. 4, as an example of a die, there are shown a case where there are 30 partition plates 21 and 15 dies 13 are formed. The partition plates 21 have the same flat plate shape and are arranged in parallel to each other so as to form a minute gap (slit) 22 to form one die 13.

The slit 22 is provided over substantially the entire width of the die 13. Further, since the plurality of dies 13 have the same shape and are arranged in parallel at a predetermined interval so that their longitudinal directions are parallel to each other, a plurality of slits 22 are provided. A slope 31 is formed on the upper part of each partition plate 21, and an acute angle opening 23 is formed by arranging the slopes 31 facing each other. The slit 22 has a role of raising the melt 24 from the lower end of each die 13 to the opening 23 by capillary action.

The aluminum oxide raw material charged into the crucible 9 is melted (raw material melt) based on the temperature rise of the crucible 9 to become a melt 24. A part of the melt 24 enters the slit 22 of the die 13, and ascends in the slit 22 based on the capillary phenomenon as described above, and is exposed from the opening 23. 25 is formed (see FIG. 7A). In the EFG method, the sapphire single crystal 1 grows according to the shape of the melt surface formed by the aluminum oxide melt pool (hereinafter referred to as “melt pool” if necessary) 25. In the die 13 shown in FIG. 4, the shape of the melt surface is an elongated rectangle, so that a flat sapphire single crystal 1 is manufactured.

Next, the seed crystal 2 will be described. As shown in FIGS. 3, 6, and 7, in the present embodiment, a plate-shaped substrate is used as the seed crystal 2, and the c-axis is along the surface direction of the main surface (a surface orthogonal to the crystal surface 29). A horizontal sapphire single crystal substrate is used. Further, the seed crystal 2 is arranged so that the plane direction of the seed crystal 2 and the longitudinal direction of the die 13 are perpendicular to each other at an angle of 90 °. Therefore, the c-axis of the seed crystal 2 is perpendicular to the partition plate 21. Also, the seed crystal 2 and the sapphire single crystal 1 are orthogonal to each other at an angle of 90 °. FIG. 3 shows the side surface of the sapphire single crystal 1.

By making the positional relationship between the planar direction of the seed crystal 2 and the longitudinal direction of the partition plate 21 perpendicular (by crossing the seed crystal 2 with the partition plate 21), the contact area between the melt 24 and the seed crystal 2 is minimized. It becomes possible to do. Therefore, the contact part of the seed crystal 2 becomes easy to become familiar with the melt 24, and the generation of crystal defects in the sapphire single crystal 1 is reduced or eliminated.

If the contact area with the substrate holder (not shown) below the shaft 17 is large, the seed crystal 2 is deformed due to stress due to a difference in thermal expansion coefficient, and may be damaged in some cases. On the contrary, the fixation of the seed crystal 2 may be loosened due to the difference in thermal expansion coefficient. Therefore, it is preferable that the contact area between the seed crystal 2 and the substrate holder is small. The seed crystal 2 needs to have a substrate shape that can be securely fixed to the substrate holder.

FIG. 5 is a view showing an example of the substrate shape of the seed crystal 2. Among these, (a) and (b) in the figure are those in which a notch 26 is provided in the upper part of the seed crystal 2. Using this notch 26, for example, a U-shaped substrate holder can be inserted from the lower side of the two notches 26, and the seed crystal 2 can be reliably held while reducing the contact area. .

Further, as shown in FIG. 5 (c), a notch hole may be provided inside the seed crystal 2. Using this cutout hole 27, for example, locking claws are inserted into the two cutout holes 27 to securely hold the seed crystal 2 while reducing the contact area between the substrate holder and the seed crystal 2. It becomes possible.

  Next, a method for manufacturing the sapphire single crystal 1 using the manufacturing apparatus 6 will be described. First, a predetermined amount of granulated aluminum oxide raw material powder (99.99% aluminum oxide), which is a sapphire raw material, is charged into a crucible 9 in which a die 13 is stored. 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 9, the heater 11 or the die 13, the inside of the growth vessel 7 is replaced with argon gas, and the oxygen concentration is set to a predetermined value or less.

  Next, the crucible 9 is heated to a predetermined temperature by the heater 11 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 9 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 24 is prepared. Further, a part of the melt 24 rises through the slit 22 of the die 13 by capillary action and reaches the surface of the die 13, and a melt pool 25 is formed on the slit 22.

  Here, in order to obtain a plurality of sapphire single crystals having the ΔTm value of 0.3 W or less according to the present invention, a temperature gradient on the upper surface of the die is set before contacting a seed crystal 2 described later with the melt. The applicant has found through verification that the following range may be set.

  Specifically, the temperature gradient (difference) between the center of each die arranged at the center of the plurality of dies and the center of each die arranged at the outermost side of the plurality of dies is 5 ° C. or more and 25 ° C. And the temperature gradient (difference) between the die center portion and the die end portions in each die is adjusted to be 0 ° C. or more and 25 ° C. or less. For this adjustment, it is sufficient to use a balance adjustment of a heat insulating material such as a heat shield so as to be within the predetermined range. Further, the temperature gradient on the upper surface of the die can be confirmed by measuring the temperature with a radiation thermometer or the like.

  Here, the length in the longitudinal direction of the die is set in the range of 1.0 cm to 26.0 cm corresponding to the width W of the straight body portion of the sapphire single crystal to be grown. Note that W is set to a value that takes into account the processing allowance for the sapphire substrate.

The thickness t of the die 13 is set in the range of 0.05 cm to 1.5 cm corresponding to the thickness t of the sapphire single crystal to be grown. The thickness t of the sapphire single crystal is set to a value that takes into account the processing allowance for the sapphire substrate.

The number of dies corresponds to the number of sapphire single crystals to be grown, and two or more dies are appropriately set in consideration of the size of the crucible, the width of the straight body of the sapphire single crystal to be grown, and mass productivity. The

As mentioned above, in multi-growth, in addition to the temperature gradient in the longitudinal direction of the die, the temperature gradient in the die alignment direction affects the dispersion of the spraying speed, and it is important to balance the two. The applicant has found by verification. It is conceivable that the temperature gradient on the upper surface of the die changes due to the influence of radiant heat between the growing crystals as the crystal growth proceeds. However, by setting the temperature gradient on the upper surface of the die before bringing the seed crystal and the melt into contact with each other within the above temperature range, it is possible to suppress variations in the spraying speed.

Next, as shown in FIGS. 6 and 7, the seed crystal 2 is lowered while being held at an angle perpendicular to the longitudinal direction of the melt reservoir 25 above the slit 22, and the seed crystal 2 is melted in the melt reservoir 25. Touch the liquid surface. The seed crystal 2 is previously introduced into the pulling container 8 from the substrate entrance 20. In FIG. 6, the melt 24 and the melt reservoir 25 are not shown in order to prioritize the visibility of the slit 22 and the opening 23.

FIG. 6 is a diagram showing the positional relationship between the seed crystal 2 and the partition plate 21. As described above, the contact area between the seed crystal 2 and the melt 24 can be reduced by making the plane direction of the seed crystal 2 orthogonal to the longitudinal direction of the partition plate 21. Accordingly, the contact portion of the seed crystal 2 becomes compatible with the melt 24, and crystal defects are less likely to occur in the grown and grown sapphire single crystal 1. Furthermore, by reducing the contact area between the melt 24 and the seed crystal 2, the neck 5 described later can be formed thinly. Also in this respect, the generation of crystal defects in the sapphire single crystal 1 is reduced or eliminated, It becomes possible to keep the crystal quality high. Therefore, the yield of the sapphire single crystal 1 can be improved.

When the seed crystal 2 is brought into contact with the melt surface, the lower part of the seed crystal 2 may be brought into contact with the upper part of the partition plate 21 and melted. FIG. 7B is a diagram showing a state in which a part of the seed crystal 2 is melted. By melting part of the seed crystal 2 in this way, the temperature difference between the seed crystal 2 and the melt 24 can be quickly eliminated, and the occurrence of crystal defects in the sapphire single crystal 1 can be further reduced. It becomes possible.

Subsequently, the substrate holder is pulled up at a predetermined rising speed to start pulling up the seed crystal 2 to form the neck portion 5 as shown in FIG. Specifically, first, the thin neck portion 5 is produced (necked) while the substrate holder is raised at high speed by the shaft 17. Hereinafter, this process is referred to as a necking process. FIG. 8 is an explanatory view showing how the neck portion 5 grows.

The neck portion 5 is a crystal portion having a thin diameter about the thickness T of the seed crystal 2 or the width of the melt pool 25, and is formed to reduce or eliminate crystal defects. Moreover, the length of the neck part 5 is formed to about 3 times the diameter. When the crystal is grown to this extent, even if a crystal defect occurs in the neck portion 5, the defect is prevented from being formed up to the sapphire single crystal 1. Therefore, by passing through the necking step, it is possible to manufacture a flat sapphire single crystal 1 in which crystal defects are reduced or eliminated.

  In order to make the necking process easier, irregularities may be provided on the lower side of the seed crystal 2. FIG. 9 is a diagram illustrating the shape of the lower side of the seed crystal 2. FIG. 9A shows the case where the lower side has a comb shape, and FIG. 9B shows the case of a saw shape.

The interval between the irregularities is matched with the interval between the openings 23, and the convex portion is aligned with the center of the melt reservoir 25. By providing the convex portion, the convex portion can be used as a growth starting point of the sapphire single crystal 1, and the neck portion 5 can be formed more easily. Note that the shape of the unevenness is not limited to that shown in FIG. 9, and may be, for example, a corrugated uneven shape.

After passing through the necking step, the heater 11 is controlled to lower the temperature of the crucible 9, and the substrate holder is set to a predetermined speed, with the seed crystal 2 as the center, as shown in FIG. The crystal 1 is grown so as to be widened in the longitudinal direction of the die 13 (spraying process). FIG. 10 is a schematic diagram showing how the width of the sapphire single crystal 1 is expanded by the spraying process.

When the sapphire single crystal 1 is widened to the full width of the die 13 (the end of the partition plate 21) (full spread), growth of a straight body portion having a width W defined by the length in the longitudinal direction of the die 13 is started. (Straight cylinder process). In the straight body process, a plurality of sapphire single crystals 1 having a straight body portion defined by side surfaces that are substantially parallel and opposed to each other are manufactured. Although the length of the straight body is not particularly limited, it is preferably 2 inches or more (50.8 mm or more). FIG. 11 is a diagram schematically showing the sapphire single crystal 1 obtained by the straight body process.

  Through the aforementioned necking step, spraying step, and straight body step, the plurality of sapphire single crystals 1 defined by the shape of the die 13 as shown in FIG. 11 are obtained.

In addition, in FIG.10 and FIG.11, the sapphire single crystal at the time of growing in the state whose temperature gradient over a biaxial direction is 0 is shown as an ideal state. However, in practice, it is difficult to set the temperature gradient in the biaxial direction to 0 as described above, and a plurality of sapphire single crystals 1 as shown in FIG. 2 are obtained.

Here, in the plurality of sapphire single crystals 1 according to the present invention, as shown in FIG. 2, the point at which the transition from the spraying portion 3 to the straight body portion 4 was started earliest is the first transition start point A, the most When the late start point is designated as the last transition start point B, the sapphire single crystal is manufactured so that the distance ΔTm between AB in the pulling direction is 0.3 W or less.

As described above, the temperature gradient of the upper surface of the die is thought to change its balance due to the influence of radiant heat between the growing crystals as the crystal growth progresses. By setting the temperature gradient to the predetermined value, a sapphire single crystal can be grown so that ΔTm is 0.3 W or less. Therefore, it becomes possible to secure a sufficient area of the straight body portion, and it is possible to improve the mass productivity and crystal quality of the sapphire single crystal. Furthermore, the mass productivity of the sapphire substrate can be improved. In addition, by suppressing the dispersion of the spraying speed, it has become possible to solve the problems related to the width of the straight body and the crystal quality, which have conventionally occurred in sapphire single crystals with extremely slow spraying speed.

As described above, since the value of ΔTm is related to the temperature gradient in the longitudinal direction of the die and the temperature gradient in the direction in which the dies are arranged, as ΔTm increases, the balance of the temperature gradient in the biaxial direction of the die increases. It can be said that it is not good. Thus, ideally, ΔTm is zero, but in practice, the temperature gradient of the die always changes during the necking and spraying steps, so in practice a slight temperature gradient across the biaxial direction is always Occur.

Thereafter, the obtained plurality of sapphire single crystals 1 are allowed to cool, the gate valve 19 is opened, moved to the pulling container 8 side, and taken out from the substrate inlet / outlet 20.

By using the manufacturing apparatus 6, the seed crystal 2, and the die 13 as described above, a plurality of sapphire single crystals 1 can be manufactured from the common seed crystal 2.

In the EFG method, a plurality of sapphire single crystals 1 are grown and grown while the plane direction of the main surface 28 of the sapphire single crystal is the same crystal direction as the crystal plane 29 of the seed crystal 2. As an example, when the seed crystal 2 is made of a sapphire single crystal and the crystal plane 29 is a c-plane, all the main surfaces 28 of the flat plate-shaped sapphire single crystal 1 to be obtained can be set as a c-plane. Therefore, it is possible to obtain a plurality of sapphire single crystals 1 with no variation in view of the crystal direction.

Therefore, the die 13 including the seed crystal 2 and the partition plate 21 needs to be positioned precisely. Therefore, as shown in FIG. 3, the manufacturing apparatus 6 is provided with a crucible driving unit 10 that rotates the crucible 9 in which the die 13 is installed, and a control unit (not shown) that controls the rotation. The shaft 17 is also provided with a shaft drive unit 18 that rotates the shaft 17 and a control unit (not shown) that controls the rotation of the shaft 17. That is, the positioning of the seed crystal 2 with respect to the die 13 is adjusted by rotating the shaft 17 or the crucible 9 by the control unit.

  The precise positioning of the seed crystal 2 and the die 13 can also be performed by using the die 13 in which a part of the slope 31 of each partition plate 21 is cut out. FIG. 12 is a view showing an example in which the notch 30 is provided in the die 13. In FIG. 12, as an example, the dies 13 each having a V-shaped cutout portion 27 at the center in the longitudinal direction of the inclined surface 31 are illustrated.

  The notch 30 is formed on a straight line in the thickness direction of the die 13. By providing such a notch 30, positioning at the time of contact between the seed crystal 2 and the melt surface is facilitated, and variations in product quality between the sapphire single crystals 1 can be reduced or eliminated. .

  Note that the crystal plane of the seed crystal 2 is not limited to the c-plane, and can be set to a desired crystal plane such as an r-plane, a-plane, or m-plane. Thus, by setting the crystal plane 29 arbitrarily, the plane direction of the main surface 28 of the sapphire single crystal 1 can be arbitrarily changed.

  Examples of the present invention will be described below. The present invention is not limited only to the following examples. A plurality of sapphire single crystals according to the present invention were manufactured using the sapphire single crystal manufacturing apparatus 6 shown in FIG.

In this example, the length of the die in the longitudinal direction was 5.5 cm, the thickness of the die was 0.3 cm, and a plurality of dies for multi-growth were set in a molybdenum crucible for crystal growth. The seed crystal used had a flat plate shape shown in FIG. 5 (a) and had a c-plane main surface, and the thickness was 0.2 cm.

Granulated high-purity aluminum oxide raw material powder (99.99%), which is a raw material of sapphire single crystal, was filled in a molybdenum crucible, and the inside of the growth vessel was filled with an argon gas atmosphere. Next, the aluminum oxide raw material powder was melted by heating with a heater, and the aluminum oxide melt was stabilized.

After the melt was stabilized, the temperature at the top of the die was measured to adjust the temperature gradient. Specifically, the temperature gradient between the center of each die arranged at the center of the plurality of dies and the center of each die arranged at the outermost side of the plurality of dies is 5 ° C. or more and 25 ° C. or less. In addition to adjustment, adjustment was performed so that the temperature gradient between the die center portion and the die end portion in each die was 5 ° C. or more and 25 ° C. or less. The adjustment was performed by adjusting the balance of a heat insulating material such as a heat shield.

Subsequently, the seed crystal was lowered to the center of the die in an arrangement perpendicular to the longitudinal direction of the die and brought into contact with the melt reservoir at the top of the die, and then the pulling was started to grow the neck portion. Subsequently, a spraying process was performed to increase the width of the single crystal while lowering the temperature of the heater.

In this spraying process, spraying of a sapphire single crystal placed near the center of a plurality of dies proceeds relatively quickly, and one of them reaches one end of the die, and growth to the straight body part is started. Was observed. The position of this first transition start point is A. As a result of continuing the spraying process, it was observed that the sapphire single crystal placed on the outermost side of multiple dies was sprayed, spraying was completed with the last one and growth to the straight body part started It was done. The position of this last transition start point is B.

Subsequently, the growth of the straight body portion of the sapphire single crystal was started to grow a plurality of sapphire single crystals. When the length of the sapphire single crystal reached a predetermined length, it was pulled up at a high speed, and the grown crystal was separated from the die.

The sapphire single crystal obtained in this example had a width W of 5.5 cm and a thickness t of 0.3 cm in the straight body portion. The distance between the first transition start point A and the last transition start point B projected in the length direction of the sapphire single crystal was 1.0 cm, and the ΔTm value was suppressed to 0.3 W or less. In this example, it was confirmed that by setting the ΔTm value to 0.3 W or less, it is possible to produce a plurality of sapphire single crystals having a straight body area sufficient for 2-inch substrate processing, which can also improve mass productivity. I found out that Further, the obtained sapphire single crystal was excellent in crystal quality without generation of crystal defects and the like.

Furthermore, by setting the ΔTm value to 0.3 W or less, it was confirmed that all the sapphire single crystals can be expanded to the full width of the die in the spraying process, and crystal growth is performed in a stable state. Thereby, it was confirmed that the variation in the thickness t between the obtained sapphire single crystals was suppressed to 0.1 t or less. It was also confirmed that the variation in the thickness t of each sapphire single crystal was suppressed to 0.10 t or less over the entire straight body portion of each sapphire single crystal.

In this example, the length of the die in the longitudinal direction was 16.0 cm, the die thickness was 0.6 cm, and a plurality of dies for multi-growth were set in a molybdenum crucible for crystal growth. The seed crystal used was a flat plate shape shown in FIG. 5 (a) and having a c-plane main surface, and the thickness was 0.25 cm.

After stabilizing the aluminum oxide melt in the same manner as in Example 1, the temperature at the top of the die was measured to adjust the temperature gradient. Specifically, the temperature gradient between the central portion of each die disposed near the center of the plurality of dies and the central portion of each die disposed on the outermost side of the plurality of dies is 5 ° or more and 25 ° or less. In addition, the temperature gradient between the die center portion and the die end portion in each die was adjusted to be 5 ° or more and 25 ° or less. This adjustment was performed by adjusting the balance of a heat insulating material such as a heat shield in the same manner as in Example 1.

Subsequently, the seed crystal was lowered to the center of the die in an arrangement perpendicular to the longitudinal direction of the die and brought into contact with the melt reservoir at the top of the die, and then the pulling was started to grow the neck portion. Subsequently, a spraying process for expanding the width of the single crystal is performed while lowering the temperature of the heater, and the growth of the straight body portion of the sapphire single crystal is started in the same manner as in Example 1 described above. Grew. When the length of the sapphire single crystal reached a predetermined length, it was pulled up at a high speed, and the grown crystal was separated from the die.

In the sapphire single crystal obtained in this example, the width W of the straight body portion was 16.0 cm and the thickness t was 0.6 cm. The distance between the first transition start point A and the last transition start point B projected in the length direction of the sapphire single crystal was 3.0 cm, and the ΔTm value was suppressed to 0.3 W or less. In this example, it was confirmed that by making the ΔTm value 0.3 W or less, it is possible to produce a plurality of sapphire single crystals having a straight body area sufficient for 6-inch substrate processing, which can also improve mass productivity. I found out that Further, the obtained sapphire single crystal was excellent in crystal quality without generation of crystal defects and the like.

Furthermore, by setting the ΔTm value to 0.3 W or less, it was confirmed that all the sapphire single crystals can be expanded to the full width of the die in the spraying process, and crystal growth is performed in a stable state. Thereby, it was confirmed that the variation in the thickness t between the obtained sapphire single crystals was suppressed to 0.1 t or less. It was also confirmed that the variation in the thickness t of each sapphire single crystal was suppressed to 0.10 t or less over the entire straight body portion of each sapphire single crystal.

1 Multiple sapphire single crystals 2 Seed crystal 3 Spraying portion 4 Straight barrel portion 5 Neck portion A First transition start point B Last transition start point W sapphire single crystal width t Sapphire single crystal thickness 6 Sapphire Single crystal manufacturing apparatus 7 Growth vessel 8 Pulling vessel 9 Crucible 10 Crucible drive unit 11 Heater 12 Electrode 13 Die 14 Heat insulating material 15 Atmospheric gas introduction port 16 Exhaust port 17 Shaft 18 Shaft drive unit 19 Gate valve 20 Substrate entrance / exit 21 Partition plate 22 Slit 23 Opening 24 Aluminum oxide melt 25 Aluminum oxide melt pool 26 Notch 27 of seed crystal 27 Notch hole 28 of seed crystal Main surface 29 Crystal surface 30 Notch 31 of partition plate Slope T Thickness of seed crystal

Claims (7)

A plurality of dies having slits are accommodated in a crucible,
Put the aluminum oxide raw material in the crucible and heat it,
Aluminum oxide raw material is melted in a crucible to prepare an aluminum oxide melt,
Form an aluminum oxide melt pool at the top of the slit through the slit,
Side surfaces that are connected substantially in parallel to each other and at least through the spraying portion from the common seed crystal by bringing the seed crystal into contact with the aluminum oxide melt at the top of the slit and pulling up the seed crystal. A method for producing a plurality of sapphire single crystals in which a straight body portion defined by the above is grown, and the width of the straight body portion is equal to a flat plate shape,
The number n of the plurality of sapphire single crystals is n ≧ 2,
Among the plurality of sapphire single crystals, the point at which the transition from the spraying part to the straight body part started earliest is the first transition start point A, the point at which the latest start is the last transition start point B,
ΔTm is an interval between the ABs in the pulling direction of the plurality of sapphire single crystals.
When the width of the straight body portion of the sapphire single crystal is W,
Before contacting the seed crystal with the aluminum oxide melt, a central portion of each die disposed in the central portion of the plurality of dies, and a central portion of each die disposed on the outermost side of the plurality of dies. The temperature gradient of 5 ° C to 25 ° C is adjusted so that the temperature gradient of the die center portion and both ends of each die is 0 ° C to 25 ° C,
The manufacturing method of the several sapphire single crystal characterized by making (DELTA) Tm value 0.3 W or less. The method for producing a plurality of sapphire single crystals according to claim 1 , wherein the ΔTm value is 0.2 W or less. The method for producing a plurality of sapphire single crystals according to claim 1 or 2 , wherein a variation in thickness t between the sapphire single crystals is 0.10 t or less. Wherein the variation of the thickness t of the sapphire single crystal, the plurality of sapphire single crystal according to any one of claims 1 to 3, characterized in that a 0.10t less in the straight body portion whole surface of the sapphire single crystal Manufacturing method. The method for producing a plurality of sapphire single crystals according to any one of claims 1 to 4 , wherein a width W of a straight body portion of the sapphire single crystals is set to 1.0 cm or more and 26.0 cm or less. Claim 1 of the width W of the straight body portion of said sapphire single crystal, 1.0 cm or more 26.0cm or less, the thickness t of the sapphire single crystal, characterized by the following 1.5cm least 0.05cm method for producing a plurality of sapphire single crystal according to any one of 1-4. According to claim 5 or 6, the width W, a manufacturing method of a plurality of single-crystal sapphire which is characterized in that less than 5.0 cm 22.0cm.

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