JPH0558793A - Method for liquid phase growth of silicon carbide and substrate holder therefor - Google Patents

Abstract

PURPOSE:To prevent sticking caused by liquid growth between a substrate and a substrate holder and to hold the substrate in stable state in a method for liquid phase growth to grow silicon carbide on the substrate by dipping a silicon carbide substrate into a molten silicon housed in a crucible. CONSTITUTION:The recessed part 30 having angle theta is formed at the place of the substrate holding part 11, 12 corresponding to the substrate in the substrate holder 27, which is used for liquid phase growth of silicon carbide. The silicon carbide substrate 21 is held at the recessed part 30 in point or line contact state. As a result, sticking of the substrate 21 with the substrate holder 27 by liquid phase growth is prevented and the substrate 21 is maintained in stable state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid phase growth method for silicon carbide and a substrate holder used for the same.

[0002]

2. Description of the Related Art Silicon carbide (SiC) is expected to be applied as a material for blue light emitting diodes.

In a light emitting diode using silicon carbide, generally, an n-type layer and a p-type layer made of carbon silicon are grown on a carbon silicon substrate to form a pn junction, and then an electrode is formed and dicing is performed. , Die bonding, wire bonding, resin molding and the like.

As a method for growing an n-type layer and a p-type layer made of silicon carbide on a silicon carbide substrate as described above, a dipping method which is one of liquid phase growth methods is widely used.
The dipping method is to saturate carbon in a silicon melt stored in a graphite crucible, and then immersing the silicon carbide substrate in the silicon melt for a predetermined growth time to grow silicon carbide on the substrate. After that, the substrate is taken out.

FIG. 5 shows an example of a liquid phase growth apparatus for silicon carbide by the dip method. Conventionally, using such an apparatus, silicon carbide is grown on a silicon carbide substrate as follows.

First, a graphite crucible 24 is charged with silicon, and a graphite lid 2 having an opening at the center is used.
5 is attached to the upper end opening of the crucible 24 and installed in the quartz tube 22. After that, the crucible 24 is heated in an inert gas atmosphere by a high-frequency induction heating method or the like to melt silicon to form a silicon melt 26, which is maintained at a high temperature and has a temperature gradient so that the inner wall of the high temperature portion of the crucible 24 is maintained. Carbon is eluted into the silicon melt 26 to saturate the carbon in the silicon melt 26.

In this state, the temperature in the vicinity of the immersed substrate 21 is measured by a radiation thermometer arranged near the wall surface 28 of the crucible 24, so that the silicon carbide substrate 21 held by the substrate holder 27 is converted into silicon. In the low temperature part of the melt 26,
By immersing in a position where a desired growth rate can be obtained, silicon carbide can be grown on silicon carbide substrate 21. After the growth of silicon carbide, the substrate 21 is attached to the substrate holder 27.
It is pulled out from the silicon melt 26, cooled to room temperature, and taken out from the quartz tube 22. Substrate 21 and substrate holder 2
Residual silicon adhering to 7 was mixed with hydrofluoric acid and nitric acid known as a solution of residual silicon (hydrofluoric acid: nitric acid = 1: 1).
By removing by 1) or the like, silicon carbide substrate 21 on which silicon carbide is grown can be obtained.

[0008]

However, after removing the residual silicon as described above, the substrate 21 and the substrate holder 27 are fixed to each other and the substrate 21 cannot be removed from the substrate holder 27, or an excessive external force is applied. There is a problem that the substrate 21 may be damaged due to the attempted removal. This is because in the liquid phase growth of silicon carbide, the silicon melt permeates into the contact portion between the substrate 21 and the substrate holder 27 during the growth, and when the silicon melt is combined with the substrate holder 27, it is deposited as silicon carbide. It is considered that this is because the holder 27 is strongly fixed to both.

In order to solve such a problem, it is conceivable to reduce the contact area between the substrate and the substrate holder. However, merely reducing the contact area hinders the stable holding of the substrate. Therefore, before or during the growth, a new problem occurs such that the substrate moves or drops from the substrate holder. Examples of growing silicon carbide on a silicon carbide substrate using the above dipping method include Journal of Applied Physics Vol. 47, No. 10, page 4546 (1976), Journal of Applied Phy.
sics 50, No. 12, page 8215 (1979), JP-A-62-69514, JP-A-2-231778.
There are documents such as the Japanese gazette.

Journal of Applied Physics No. 47 above
Volume 10, p. 4546 (1976), and Journal
In L of Applied Physics, Vol. 50, No. 12, page 8215 (1979), a substrate holder 27 as shown in FIG. 5 is used, which is disclosed in JP-A-62-69514 and JP-A-2-231778. FIG. 6 in the publication
A substrate holder 27 as shown in is used. In any case, it has succeeded in growing silicon carbide on the silicon carbide substrate 21. However, in any case, the problem that the substrate 21 and the substrate holder 27 are fixed to each other as described above, and the method for solving such a problem while holding the substrate 21 in a stable state are not described. Not not.

According to the present invention, in a liquid phase growth method in which a silicon carbide substrate is immersed in a silicon melt contained in a crucible to grow silicon carbide on the substrate, sticking between the substrate and a substrate holder is prevented. In addition, it is an object of the present invention to provide a liquid phase growth method capable of holding a substrate in a stable state and a substrate holder used for the same.

[0012]

SUMMARY OF THE INVENTION The present invention is a liquid phase growth method for growing silicon carbide on a silicon carbide substrate by immersing the silicon carbide substrate in a silicon melt. A substrate holder held by contact is immersed in a silicon melt while holding the substrate to grow silicon carbide on the substrate, and then the substrate holder pulls up the substrate from the silicon melt to separate the substrate from the substrate holder. Is.

Further, the substrate holder of the present invention used for a liquid phase growth method of holding a silicon carbide substrate and immersing the substrate in a silicon melt to grow silicon carbide on the substrate is a substrate holding device for holding a substrate. A concave portion is formed in the portion, and the substrate is held in a state where the substrate end portion is in point contact or line contact in the concave portion.

[0014]

According to the present invention, the carbon-silicon substrate held by the substrate holder is immersed in the silicon melt contained in the crucible to cause liquid-phase growth of silicon carbide on the substrate, and then the substrate is Separate from the substrate holder. The substrate holder has a concave portion formed in the substrate holding portion for holding the substrate, and holds the substrate in a state in which the substrate ends are in point contact or line contact with each other in the concave portion. ,
Moreover, the substrate can be held in a stable state.

[0015]

Embodiments of the present invention will be described in detail below with reference to the drawings.

1 to 4 show an embodiment of a substrate holder according to the present invention. Substrate holder 2 shown in FIG.
7 is an enlarged view of the substrate holder 27 shown in FIG. 2. The substrate holder 27 is formed in a cylindrical shape as shown in the cross section in FIG.
The silicon carbide substrate 21 is held by being sandwiched by. Substrate holder 27 is provided with recess 30 having a triangular cross section at a position corresponding to the periphery of the end of silicon carbide substrate 21. The concave portion 30 has an angle θ facing the substrate 21, and as shown in the drawing, the two inclined surfaces 31 sandwich the end portion of the substrate 21 in line contact.

The substrate holder 27 shown in FIG.
1 has a semicircular cross section at a position corresponding to the periphery of the end of
Have two. In this embodiment, the semicircular recess 32
The end portion of the substrate 21 is sandwiched by the line contact.

The substrate holder 27 shown in FIG.
1 has a trapezoidal cross section at a portion corresponding to the periphery of one end.
The two end faces of the substrate 21 are held in line contact by the two trapezoidal inclined surfaces 34.

Liquid crystal growth of silicon carbide is performed by the dipping method using the substrate holder 27. For liquid phase growth, an apparatus as shown in FIG. 5 is used to grow silicon carbide on a silicon carbide substrate as follows.

First, silicon is charged into a graphite crucible 24, a graphite lid 25 having an opening at the center is attached to the upper end opening of the crucible 24, and a quartz tube 22 is provided.
Install inside. After that, the crucible 24 is heated in an inert gas atmosphere by a high frequency induction heating method or the like to melt silicon to form a silicon melt 26, which is maintained at a high temperature and has a temperature gradient so that the inner wall of the high temperature portion of the crucible 24 is maintained. Carbon is eluted into the silicon melt 26 to saturate the carbon in the silicon melt 26.

In this state, the silicon carbide substrate 21 held by the substrate holder 27 is immersed in a low temperature portion of the silicon melt 26 at a position where a desired growth rate can be obtained.
Silicon carbide can be grown on silicon carbide substrate 21. After the growth of silicon carbide, the substrate 21 is pulled up from the silicon melt 26 by the substrate holder 27, cooled to room temperature, and taken out from the quartz tube 22. The residual silicon adhering to the substrate 21 and the substrate holder 27 is a mixed solution of hydrofluoric acid and nitric acid known as a solution of residual silicon (hydrofluoric acid: nitric acid = 1: 1).
The silicon carbide substrate 21 on which silicon carbide is grown can be obtained by removing the silicon carbide substrate 21 with the above method.

Conventionally, the substrate 2 is removed after the residual silicon is removed.
1 and the substrate holder 27 are fixed to each other, and the substrate 21 cannot be removed from the substrate holder 27, or the substrate 21 is damaged by attempting to remove it by an excessive external force. This is because in the liquid phase growth of silicon carbide, the silicon melt permeates into the contact portion between the substrate 21 and the substrate holder 27 during the growth, and when the silicon melt is combined with the substrate holder 27, it is deposited as silicon carbide. It is considered that this is because the holder 27 is strongly fixed to both.

According to the present invention, in any of the above substrate holders 27, the substrate 21 and the substrate holder 27 are in point contact or line contact, so that the substrate 21 and the substrate holder 27 are fixed by liquid phase growth. The area is reduced and therefore the total sticking force is reduced. Also, the recesses 30, 32, 33
Since the substrate 21 is held by, the substrate 21 is held in a stable state, and problems such as movement and dropping do not occur.

When holding the silicon carbide substrate 21 by the substrate holder 27, in order to make point contact, the recess 3 is formed.
This can be achieved by setting 0, 32, and 33 as not having a uniform depth but having a gentle curve as a whole.

The substrate holder 27 according to the present invention is shown in FIGS.
The substrate 21 is not limited to the shape as shown in FIG. If it is satisfied that the substrate 21 and the substrate holder 27 are in point contact or line contact, and that the substrate 21 is held in a stable state, the substrate holder 27 is respectively attached to corresponding portions of the substrate holding portion. The shape of the concave portion provided is arbitrary. However, the shape shown in FIG. 1 or 3 is preferable in consideration of the ease of processing. Further, in the case of the substrate holder 27 shown in FIG. 1, there is no particular restriction on the angle θ, but if θ is too large, the holding of the substrate 21 becomes unstable, and if θ is too small, the substrate holder 27 must be made thick. Because it will not be
The value of θ is preferably 70 degrees or more and 110 degrees or less,
More preferably, it is 90 degrees.

Next, specific examples according to the present invention will be shown.

(Specific Example 1) In a liquid phase growth apparatus as shown in FIG. 5, a substrate holder 27 (θ = 90 degrees) provided with a recess 30 having a triangular cross section as shown in FIG.
Silicon carbide was grown on a 0 mm × 10 mm × 1 mm silicon carbide substrate 21 under the conditions of a growth temperature of 1720 ° C. and a growth rate of 6 μm / hour for 3 hours. In addition, crucible 2
The temperature in the vicinity of the immersed substrate 21 on the wall surface of No. 4 was measured with a radiation thermometer, and this was used as the growth temperature.

The substrate 21 is stably held by the substrate holder 27, and there is no problem that it moves or drops before or during the growth. After the growth of silicon carbide on the silicon carbide substrate 21, the substrate 21 together with the substrate holder 27 is pulled out from the silicon melt, cooled to room temperature and taken out, and the residual silicon adhering to the substrate 21 and the substrate holder 27 is hydrofluoric acid: When the substrate 21 was removed with a mixed solution of nitric acid = 1: 1, the substrate 21 could be easily removed from the substrate holder 27.

(Specific Example 2) In a liquid phase growth apparatus as shown in FIG. 5, a substrate holder 27 (a radius of curvature of the concave portion = 1 mm) provided with a concave portion 32 having a semicircular cross section as shown in FIG. 3 is used. On a silicon carbide substrate 21 of 10 mm × 10 mm × 1 mm, a growth temperature of 1720 ° C. and a growth rate of 6 μm / ho
Under the condition of ur, silicon carbide was grown for 3 hours. The temperature in the vicinity of the immersed substrate 21 on the wall surface of the crucible 24 was measured with a radiation thermometer, and this was used as the growth temperature.

The substrate 21 is stably held by the substrate holder 27, and there is no problem that it moves or drops before or during growth. After the growth of silicon carbide on the silicon carbide substrate 21, the substrate 21 together with the substrate holder 27 is pulled out from the silicon melt, cooled to room temperature and taken out, and the residual silicon adhering to the substrate 21 and the substrate holder 27 is hydrofluoric acid: When the substrate 21 was removed with a mixed solution of nitric acid = 1: 1, the substrate 21 could be easily removed from the substrate holder 27.

[0031]

As described above, according to the present invention, in the liquid phase growth method of silicon carbide, the recess is formed in the substrate holding portion of the substrate holder, and the end of the substrate is point-contacted or line-contacted in the recess. The substrate is held in this state.
Therefore, the substrate can be held in a stable state, the substrate and the substrate holder can be prevented from sticking to each other due to liquid phase growth, and the substrate can be easily removed from the substrate holder.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a substrate holder according to the present invention.

FIG. 2 is a sectional view showing an embodiment of a liquid phase growth apparatus used in the present invention.

FIG. 3 is a sectional view showing another embodiment of the substrate holder according to the present invention.

FIG. 4 is a sectional view showing another embodiment of the substrate holder according to the present invention.

FIG. 5 is a cross-sectional view showing an example of use of a liquid phase growth apparatus for silicon carbide.

FIG. 6 is a sectional view showing an example of a conventional liquid phase growth apparatus for silicon carbide.

[Explanation of symbols]

 11 substrate holding part 12 substrate holding part 21 silicon carbide substrate 22 quartz tube 23 high frequency coil 24 crucible 25 lid 26 silicon melt 27 substrate holder 28 wall surface 30, 32, 33 recess

Claims (3)

[Claims] 1. A liquid phase growth method for growing silicon carbide on a silicon carbide substrate by immersing the substrate in a silicon melt, wherein a substrate holder having a recess formed in a substrate holding portion is used. Is immersed in the silicon melt while holding the substrate in a state where the end portion of the substrate is in point contact or line contact in the concave portion of the substrate holder, and after growing silicon carbide on the substrate, the substrate holder A liquid phase growth method comprising pulling a substrate out of the silicon melt and detaching the substrate from the substrate holder. 2. A substrate holder used in a liquid phase growth method for holding a silicon carbide substrate and immersing the substrate in a silicon melt to grow silicon carbide on the substrate.
The substrate holder is configured such that a recess is formed in a substrate holding portion that holds the substrate, and the substrate is held in a state where the substrate end is in point or line contact in the recess. Substrate holder for liquid phase growth. 3. The substrate holder for liquid phase growth according to claim 2, wherein the recess has a triangular cross section.