JPH08274038A - Liquid phase epitaxial growth method and growth device for the method - Google Patents

Abstract

PURPOSE: To provide a liquid phase epitaxial growth method, which grows a thick and uniform epitaxial layer with good quality in a short time and can cope with also in the mass production manner of the epitaxial layer, and a growth device for the epitaxial growth method. CONSTITUTION: A growth chamber 3 with a seed substrate 1 held in a vertically placed state thereon is provided on a freely rotatable slider 5 formed into a cylindrical form. After a melt 7 is introduced from a melt tank 6 into a growth chamber 3, the slider 5 is rotated 90 deg. to grow epitaxially the seed substrate 1 in a laterally placed state. When the epitaxial growth ends, the slider 5 is further rotated 90 deg. to discharge the melt 7 in a waste liquor tank 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid phase epitaxial growth method and a growth apparatus for use in a light emitting diode epitaxial wafer manufacturing process, and more particularly to a liquid phase epitaxial growth apparatus for growing a compound semiconductor epitaxial growth layer thickly and uniformly in a short time. Regarding

[0002]

2. Description of the Related Art On a III-V compound semiconductor substrate, gallium arsenide (hereinafter referred to as GaAs), gallium aluminum arsenide (hereinafter referred to as GaAlAs), gallium phosphide (hereinafter referred to as GaP), or the like of high quality is used. A liquid phase epitaxial growth method is one of means for obtaining an epitaxial layer. In the liquid phase epitaxial growth method using gallium (hereinafter, referred to as Ga) as a solvent, generally, a horizontal wafer slide boat method is the mainstream.

A liquid boat epitaxial growth apparatus of a horizontal wafer slide boat system will be described below. FIG. 5 is a schematic lateral cross-sectional view of a laterally mounted slide boat type liquid phase epitaxial growth apparatus. In FIG. 5, 50
Is a seed substrate, 51 is a pedestal for holding the seed substrate 50, 52 is a freely slidable melt bath disposed on the pedestal 51, 53 is a melt, and 54 is an electric furnace.

An example of liquid phase epitaxial growth of GaAs using this apparatus will be described below.
Ga is used as a solvent and polycrystalline Ga is used as a solute.
After adding As and, if necessary, a small amount of active impurities, the melt bath 52 is heated in an electric furnace 54 to melt 53.
To form.

After that, when the melt 53 reaches a predetermined temperature, the melt tank 52 is moved in the direction of the arrow B, and the temperature of the melt 53 is kept constant while the melt 53 is in contact with the seed substrate 50. When gradually cooled at a temperature of ℃ / min), the melt 53
The supersaturated component GaAs existing inside is deposited on the seed substrate 50 to form a single crystal. This is liquid phase epitaxial growth. The epitaxial growth is stopped by separating the seed substrate 50 and the melt 53.

However, this method has a problem in mass productivity because only one or two seed substrates 50 for epitaxial growth can be set. In addition, the seed substrate 50 and the melt 5
When it is cut off from the substrate 3, mechanical damage may occur on the surface of the seed substrate 50. In consideration of this point, the vertical wafer slide boat method is adopted.

The wafer vertical slide boat system will be described below. FIG. 6 is a schematic side cross-sectional view of a vertical boat slide boat type liquid phase epitaxial growth apparatus. In FIG. 6, 55 is a holder, 56 is a growth chamber, and 57.
Is a waste liquid tank. Further, in FIG. 6, the same members as those in FIG. 5 are designated by the same reference numerals and the description thereof will be omitted.

In this system, a growth chamber 56 is used instead of a pedestal, a large number of seed substrates 50 are vertically fixed to a holder 55 in the growth chamber 56, and a melt 53 is introduced into the growth chamber 56. Epitaxial growth is carried out, and at the end, the melt 53 is discharged into the waste liquid tank 57 to separate the seed substrate 50 and the melt 53. This method is suitable for mass production because it can hold several to several tens of substrates.

[0009]

In these liquid phase epitaxial growth methods, the crystal growth rate is determined by the solute diffusion rate control. However, in actual liquid phase epitaxial growth, a difference in concentration between the solvent and the solute occurs in the vertical direction of the melt 53 in the melt tank 52 or the growth chamber 56 due to the difference in specific gravity between the solvent and the solute. Thus, in the horizontal wafer slide boat method, the seed substrate 50 is held below the melt 53, so that the crystal growth rate becomes slow. Therefore, a wide temperature difference is required and it takes a long time to grow the epitaxial layer thickly by the horizontal wafer slide boat method.

On the other hand, in the vertical wafer slide boat method, it is possible to grow thicker than in the horizontal wafer slide boat method, but as described above, there is a difference in concentration in the vertical direction of the melt 53 in the growth chamber 56. As a result, the obtained epitaxial layer is thick in the upper part of the seed substrate 50 and thin in the lower part.
That is, the epitaxial layer has a large variation in thickness, and it is difficult to obtain a thick and uniform epitaxial layer.

In view of the above, it is an object of the present invention to provide a liquid phase epitaxial growth method and a growth apparatus capable of growing a thick and uniform epitaxial layer with high quality in a short time and being compatible with mass production.

[0012]

In order to achieve the above object, the present invention provides a semiconductor substrate in which a melt is introduced into a growth chamber in which a semiconductor substrate is held vertically and then the semiconductor substrate is placed horizontally. It is for epitaxial growth on the surface.

Specifically, the solution means taken by the invention of claim 1 is a liquid phase epitaxial growth method, in which a melt is introduced into a growth chamber in which a semiconductor substrate is held vertically, and the semiconductor substrate is The configuration includes a step of changing from a vertically placed state to a horizontally placed state, and a step of forming an epitaxial layer on the surface of the semiconductor substrate in the horizontally placed state.

Specifically, the solution means taken by the invention of claim 2 is that a liquid phase epitaxial growth apparatus holds a semiconductor substrate and a growth chamber for epitaxially growing the semiconductor substrate on the surface of the held semiconductor substrate; And a rotation means for rotating the shaft.

Specifically, a solution means taken by the invention of claim 3 is that a liquid phase epitaxial growth apparatus is provided with a slider provided so as to be movable in the horizontal direction and rotatable about an axis in the horizontal direction, and the slider. And a growth chamber for holding the semiconductor substrate and performing epitaxial growth on the surface of the held semiconductor substrate.

According to a fourth aspect of the invention, in addition to the structure of the third aspect, the slider is formed in a columnar shape extending in the horizontal direction and is provided rotatably around its central axis. It is a thing.

[0017]

According to the structure of the present invention, since the semiconductor substrates are held vertically, a large number of semiconductor substrates can be accommodated in the same area, and the semiconductor substrates are epitaxially grown horizontally in a melt portion having a high solute concentration. As a result, a thick and uniform epitaxial layer can be formed.

According to the structure of claim 2, since the growth chamber for holding the semiconductor substrate in a vertical position is rotated about a horizontal axis, the semiconductor substrate is epitaxially grown in a horizontal position in a melt portion having a high solute concentration. By doing so, a thick and uniform epitaxial layer can be formed. Further, if the semiconductor substrate is rotated in the opposite direction and the semiconductor substrate is laterally laid on a melt portion having a low solute concentration in a horizontal state, a thin and uniform epitaxial layer can be formed.

According to the structure of claim 3, since the slider having the growth chamber for holding the semiconductor substrate in a vertical position is provided so as to be movable in the horizontal direction and rotatable about the axis in the horizontal direction, the growth chamber is The slider can be introduced horizontally from the melt tank to the growth chamber by approaching the melt tank, or the melt can be discharged from the growth chamber to the waste tank by approaching the growth chamber to the waste tank and the slider can be moved horizontally. The semiconductor substrate housed in the growth chamber can be placed vertically or horizontally by rotating it about the axis.

According to the structure of claim 4, since the slider is formed in a columnar shape extending in the horizontal direction and is rotatably provided around its central axis, by rotating the slider about its central axis, The semiconductor substrate in the growth chamber can be placed vertically or horizontally.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1A is a schematic side sectional view of a liquid phase epitaxial growth apparatus according to an embodiment of the present invention.
(B) is a schematic longitudinal sectional view of the liquid phase epitaxial growth apparatus. FIG. 2 is a diagram showing the state of the substrate and the melt in the growth chamber in each step of liquid phase epitaxial growth.

In FIGS. 1 and 2, 1 is a seed substrate, 2 is a holder for holding the seed substrate 1, 3 is a growth chamber, and 4 is a growth chamber 3.
A melted liquid port provided in, a rotatable slider made of graphite, 6 a melted liquid tank, 7 a melted liquid, and 8 a waste liquid tank.

As shown in FIG. 1, this apparatus comprises a melt bath 6 for containing a melt 7 which is a material for epitaxial growth,
A waste liquid tank 8 for dropping the melt 7 after the growth and a melt tank 6
And seed substrate 1 epitaxially grown between the waste liquid tank 8
And a slider 5 having a growth chamber 3 for holding The slider 5 has a cylindrical shape having an axis parallel to the moving direction A, and is rotatable around the axis. The growth chamber 3 has a melt port 4 that serves as both introduction and discharge of the melt 7, and the seed substrate 1 is held in the growth chamber 3 by a holder 2 so that the axis of the slider 5 and the substrate surface are parallel to each other. ing.

As an example, a P-type substrate doped with Zn is used as the seed substrate 1, and Ga is used as a solvent and Al is used as a solute.
And a molten liquid 7 which was weighed so that the Al composition ratio was 75%, and Ga _1-x Al _x As (x =
A case of forming a 0.75) ternary mixed crystal epitaxial layer will be described with reference to FIG.

The liquid phase epitaxial growth apparatus in which the seed substrate 1 and the melt 7 are charged is heated to a predetermined temperature at which the solute is saturated with the solvent in an electric furnace (not shown) in a hydrogen atmosphere of high purity. At this time, the seed substrate 1 is placed vertically, that is, in a state of being placed vertically, with the seed substrate 1 attached to the right side of the holder 2 (FIG. 2A).

After that, when the melt 7 reaches a predetermined temperature at which the melt 7 comes into contact with the seed substrate 1, the slider 5 is pulled in the direction of arrow A, and the melt 7 is introduced into the growth chamber 3 through the melt port 4 to form the seed. Contact with the substrate 1. When the melt 7 fills the growth chamber 3, the slider 5 is rotated clockwise by 90 °. At this time, the seed substrate 1 is horizontal, that is, in a horizontal position,
Moreover, it is held on the upper side with respect to the melt 7 (FIG. 2B).

In this state, the temperature is kept at a constant cooling rate, for example, 1
Epitaxial growth starts when the material is gradually cooled at ° C / min. After that, when the temperature reached the end of epitaxial growth, slide the slider 5 further clockwise.
The seed substrate 1 is rotated vertically by 0 ° so that the seed substrate 1 is vertically attached to the left side of the holder 2 (FIG. 2C).

At this time, the melt port 4 faces downward. Pull the slider 5 in the direction of arrow A, and set the melt port 4 to the waste liquid tank 8
Then, the melt 7 is discharged and the epitaxial growth is completed.

Although the epitaxial growth step for only one layer is described here, when growing a plurality of epitaxial layers, it is sufficient to prepare the melts for the number of layers to be grown and repeat the above-described embodiment a necessary number of times.

FIG. 3 shows the relationship between the height of the melt 7 in the epitaxial growth state and the concentration distribution in the melt 7 in this embodiment. The seed substrate 1 is held above the melt 7 during the process of growing the epitaxial layer. On the other hand, the melt 7 in the growth chamber 3 has a concentration distribution in the solute and the solvent. As shown in the figure, it can be seen that the solute concentration is high just below the seed substrate 1.

Since the epitaxial growth rate is determined by the diffusion rate control of the solute, there are many diffusion sources immediately below the seed substrate 1 and the diffusion distance is short. Therefore, the growth rate of the epitaxial layer is higher than that when the seed substrate 1 is held below the growth chamber 3. In addition, since the solute concentration distribution immediately below the seed substrate 1 is uniform because it is placed horizontally, the variation in the thickness of the epitaxial layer on the same substrate, which is seen in the wafer vertical placement slide boat method, is also improved.

Further, by making the slider 5 rotatable, that is, the growth chamber 3 and the seed substrate 1, the wafers can be placed vertically when the melt 7 is introduced and discharged, so that various wafers can be grown at the same time. The melt can be introduced uniformly between the substrates 1. Further, even when discharged, the seed substrate 1 is not mechanically damaged and the melt 7 remaining in the growth chamber 3 can be removed, and a high-quality epitaxial layer can be obtained.

Finally, FIG. 4 is a comparative graph showing the thickness and variation of the thickness of the epitaxial layer grown by the conventional liquid phase epitaxial growth apparatus and the epitaxial layer grown by the liquid phase epitaxial growth apparatus according to one embodiment of the present invention. Shown in.

As shown in FIG. 4, the epitaxial layer thickness of the seed substrate 1 obtained by the liquid phase epitaxial growth apparatus according to the embodiment of the present invention is about three times as large as that of the horizontal wafer slide boat method (epitaxial growth at the same time). Do)
It can be seen that the thickness variation is equal to or more than the result obtained by the horizontal wafer slide boat method.

Here, an example in which the seed substrate 1 is arranged on the upper portion of the molten liquid to perform epitaxial growth is explained mainly for the purpose of increasing the thickness of the epitaxial layer. , If the rotation of the slider 5 is reversed, that is, counterclockwise, the seed substrate 1 will melt 7
Therefore, it is possible to uniformly form both thick and thin layers with the same device.

[0036]

According to the liquid phase epitaxial growth method of the first aspect of the present invention, since a large number of semiconductor substrates can be accommodated, the mass productivity is excellent, and at the time of epitaxial growth, the semiconductor substrates are epitaxially grown horizontally. Therefore, a thick and uniform epitaxial layer can be obtained for many substrates.

According to the liquid phase epitaxial growth apparatus of the second aspect of the present invention, since the growth chamber for holding the semiconductor substrate in the vertical state is rotated about the horizontal axis, the semiconductor substrate can be stored in the vertical state. Epitaxial growth can be performed on a semiconductor substrate in a horizontal position. Therefore, a substrate on which a thick and uniform epitaxial layer is formed can be manufactured with good mass productivity. Therefore, it is possible to provide a light emitting diode that is inexpensive and has excellent performance.

According to the liquid phase epitaxial growth apparatus of the third aspect of the present invention, the slider having the growth chamber for holding the semiconductor substrate in a vertical position moves in the horizontal direction and rotates about the horizontal axis. By utilizing the advantages of both the horizontal slide boat method and the vertical slide boat method, it is possible to mass-produce a substrate on which a thick and uniform epitaxial layer is formed and a substrate on which a thin and uniform epitaxial layer is formed.

According to the liquid phase epitaxial growth apparatus of the fourth aspect of the present invention, since the slider is formed in a columnar shape extending in the horizontal direction and rotates about its central axis, the conventional horizontal slide boat system and vertical slide system are used. It is possible to make the device compact by making use of the advantages of both boat types.

[Brief description of drawings]

FIG. 1A is a schematic side sectional view of a liquid phase epitaxial growth apparatus according to an embodiment of the present invention. (B) It is a schematic longitudinal cross-sectional view of the liquid phase epitaxial growth apparatus which concerns on one Example of this invention.

FIG. 2 is a diagram showing a state of a substrate and a melt in a growth chamber in a liquid phase epitaxial growth process according to an example of the present invention.

FIG. 3 is a diagram showing the relationship between the height of the melt in the epitaxial growth state and the concentration distribution in the melt in this example.

FIG. 4 is a comparative graph of the thickness and variation in thickness of an epitaxial layer grown by a conventional liquid phase epitaxial growth apparatus and an epitaxial layer grown by a liquid phase epitaxial growth apparatus according to an embodiment of the present invention.

FIG. 5 is a schematic side sectional view of a conventional wafer lateral slide boat type liquid phase epitaxial growth apparatus.

FIG. 6 is a schematic lateral cross-sectional view of a conventional wafer vertical slide boat type liquid phase epitaxial growth apparatus.

[Explanation of symbols]

 1 type substrate 2 holding tool 3 growth chamber 4 melting liquid port 5 slider 6 melting liquid tank 7 melting liquid 8 waste liquid tank 50 seed substrate 51 mount 52 melting liquid tank 53 melting liquid 54 electric furnace 55 holding tool 56 growth chamber 57 waste liquid tank

Claims (4)

[Claims] 1. A step of introducing a melt into a growth chamber holding a semiconductor substrate in a vertical state, a step of changing the semiconductor substrate from a vertical state to a horizontal state, and a semiconductor substrate in a horizontal state. And a step of forming an epitaxial layer on the surface of the liquid phase epitaxial growth method. 2. A liquid comprising: a growth chamber for holding a semiconductor substrate and performing epitaxial growth on the surface of the held semiconductor substrate; and a rotating means for rotating the growth chamber about a horizontal axis. Phase epitaxial growth system. 3. A slider provided horizontally movable and rotatable about a horizontal axis, and a growth chamber provided on the slider for holding a semiconductor substrate and performing epitaxial growth on the surface of the held semiconductor substrate. And a liquid phase epitaxial growth apparatus comprising: 4. The liquid phase epitaxial growth apparatus according to claim 3, wherein the slider is formed in a columnar shape that extends in the horizontal direction and is rotatably provided around its central axis.