JP3495910B2 - Liquid phase epitaxial growth equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION The present invention relates to III-
The present invention relates to a liquid phase epitaxial growth apparatus for group V compound semiconductors, and more particularly to a liquid phase epitaxial growth apparatus for growing GaAs crystals.

[0002]

2. Description of the Related Art A general structure of a conventional liquid phase epitaxial growth apparatus for mass production is shown in FIGS. FIG. 8 is an external perspective view of a conventional liquid phase epitaxial growth apparatus,
9 is a cross-sectional view of a conventional liquid phase epitaxial growth apparatus before growth, FIG. 10 is a cross-sectional view of a conventional liquid phase epitaxial growth apparatus during growth, and FIG. It is a longitudinal cross-sectional view of the liquid phase epitaxial growth apparatus during growth.

In FIG. 8, a liquid phase epitaxial growth apparatus 50 comprises a growth boat storage member 53 for accommodating a growth boat 51 and an upper member 54 thereon, and an operation rod (rotation / movement) 52. . 55 is a melt drop port.

9 and 10 are cross-sectional views of a liquid phase epitaxial growth apparatus 50. FIG. 9 shows a state before growth, FIG. 10 shows a state during growth, and FIG. 11 shows a conventional method. It is a longitudinal cross-sectional view of an example liquid phase epitaxial growth apparatus 50.

In FIG. 9, inside the growth boat 51,
Rotor part 59, GaAs substrate 60 for growth, and growth chamber 61
There is. The rotor part 59 includes a rotor end 56, a rotor bar 57, a substrate holding plate 58, and the like, and a GaAs substrate 60 for growth is held in close contact with the substrate holding plate 58. 52 is a control rod (rotation / movement), 5
4 is an upper member, 55 is a melt drop port, 62 is a melt, and 63 is a melt reservoir.

In FIG. 10, 50 is a liquid phase epitaxial growth apparatus, 51 is a growth boat, 52 is an operating rod (rotation / movement), 53 is a growth boat storage member, 54 is an upper member, and 55 is a melt drop. A port, 56 is a rotor end, 57 is a rotor bar, 58 is a substrate holding plate, 59 is a rotor part, 60 is a growth GaAs substrate, 61 is a growth chamber, 62 is a melt, and 63 is a melt reservoir.

FIG. 11 is a vertical sectional view of the liquid phase epitaxial growth apparatus 50 taken along the line BB 'in FIG.
In FIG. 11, 50 is a liquid phase epitaxial growth apparatus,
Reference numeral 51 is a growth boat, 53 is a growth boat storage member, and 5
4 is an upper member, 57 is a rotor bar, 58 is a substrate holding plate, 60 is a GaAs substrate for growth, 61 is a growth chamber, 62 is a melt, and 63 is a melt reservoir.

Next, a conventional liquid phase epitaxial growth method will be described with reference to FIGS. 9 and 10. In FIG. 9, the growth GaAs substrate 60 is a substrate holding plate 58.
Is closely adhered to and is held in the growth chamber 61. In the conventional example, a plurality of sheets (50-
Crystal growth is carried out by disposing 100 growth GaAs substrates 60. The melt 62 is disposed in the melt reservoir 63 of the upper member 54, and the melt drop port 55 is closed by the upper wall 51 a of the growth boat 51.

[Procedure for Crystal Growth] (1) Substrate Setting Step A GaAs substrate 60 is arranged so that the back surface of the substrate holding plate 58 is in contact with the rotor end 56 and the rotor bar 5.
7. Assemble the supporting interior parts such as the rotor part 59.

(2) Pre-growth step In the growth chamber 61, the GaAs substrate 60 and the rotor section 5 are provided.
After putting 9 etc., store in the growth boat storage member 53,
The upper member 54 is placed on top of it, and the raw materials Ga and GaAs are placed.
The polycrystal and the Si for doping are set in the melt reservoir 63, and the operation rod (rotation / movement) 52 is set to obtain the state of FIG. This conductor liquid phase epitaxial growth apparatus 50 is loaded into a quartz tube in an electric furnace and placed in a hydrogen gas atmosphere. The electric furnace that is controlled to a predetermined temperature has a high temperature (usually 900-1
The temperature is raised to 000 ° C.) to sufficiently melt the raw material.

(3) Growth process In FIG. 9, when the operating rod 52 is moved to the left, the upper wall 51 of the growth boat 51 that has closed the melt drop port 55.
a moves to the left, the melt drop port 55 is opened, and the melt 6
2 drops into the lower growth chamber 61 and becomes the state of FIG.
By rotating the operation rod (rotation / movement) 52, the temperature of the electric furnace is gradually lowered while rotating the rotor portion 59 connected to the operation rod, and the GaAs crystal is grown on the surface of the GaAs substrate 60. At this time, the rotation speed of the rotor portion 59 is about 0.5 to 2.0 rotations / minute.

[0012]

However, in such a conventional liquid phase epitaxial growth apparatus, the rotation causes the substrate to constantly rotate and move in the vertical direction in the growth chamber. It is effective not to be affected by the difference in the concentration of atoms (As) that controls the crystal growth of the melt that occurs, and to make the growth film thickness of GaAs crystallized on the substrate uniform within the surface, while GaAs is grown during the temperature decrease. The GaAs crystals deposited on the rotor end 56 other than the substrate 60, the rotor bar 57, the substrate holding plate 58, and the like, such as the rotor portion, rotate to melt 6 between the GaAs substrate 60 and the GaAs substrate 60.
2 becomes a growth nucleus and interferes with the normal growth of GaAs crystal on the GaAs substrate 60, and causes a dent (a thin growth film portion) on the surface of the epitaxial wafer after the crystal growth is completed. there were.

This is because the nuclei of GaAs crystals grow in the melt between the substrates, so that the solute (GaAs component) in the melt (Ga component + GaAs component) that should have been taken in on the base slope is taken away. There is. That is, in the vicinity of the presence of unnecessary crystal nuclei, the growth on the normal GaAs substrate 60 is slower than in the area where the unnecessary crystal nuclei are not present, and as a result, the thickness of the GaAs crystal growth film is locally reduced. .

Since the dented portion has abnormal growth and the film thickness is not normal, not only the variation of the electrical characteristics is increased, but also many pinholes are provided around the dented portion for alleviating the step difference in the film thickness. It exists and is a cause of a large leakage current in electrical characteristics.

In order to solve such a problem, the present invention aims to obtain an epitaxial wafer having a smooth surface state and stable characteristics by reducing unnecessary GaAs crystal nuclei which cause dents as much as possible. .

[0016]

In a liquid phase epitaxial growth apparatus according to claim 1 of the present invention, an upper member having a melt reservoir for storing a melt of a crystal raw material and a growth chamber for accommodating a substrate are provided. In the electric furnace heated to a constant temperature, the melt stored in the melt reservoir is dropped into the growth chamber, and then cooled to crystallize on the substrate surface. Is a liquid phase epitaxial growth apparatus for growing a substrate, and a growth chamber formed in a growth boat is partitioned by a substrate holding plate into two or one substrates. distribution but with is arranged to be in contact, with the melt through the growth disposed the melt inlet to the boat to the growth chamber is injected, the melt of the liquid leakage prevention ring growth chamber It is characterized by being installed.

Further, the liquid phase epitaxial growth apparatus according to a first aspect of the present invention, the dimensions of the cross section of said growth chamber (inner <br/> diameter), than the outer diameter of the substrate surface in contact with the melt , + 0-5
It is characterized by having a size of about mm or less.

Further, in the liquid phase epitaxial growth apparatus according to claim 2 of the present invention, the volume of the growth chamber partitioned by the substrate holding plate is 0.3 cc / cm ² or less per unit area of the growth substrate. It is characterized by being.

[0019]

1 to 7 are views relating to an embodiment of the present invention. First, a GaAs substrate for growth and a G
Amount of melt V between aAs substrates and the number of dents in one liquid phase epitaxial growth (referred to as one batch) of a plurality of (50 to 100) GaAs substrates for growth (the number of thinly grown portions) 6) shows the result of the embodiment of the present invention performed on the correlation with the total N of FIG.

In FIG. 6, the horizontal axis represents the melt volume V (unit: g) per substrate, and the vertical axis represents the total number N (unit: pieces) of the number of dents (the number of portions where the grown film thickness is thin). ) Is shown. Figure 6
As shown in, the melt amount V per substrate is 30 g.
(Our condition) In the following cases, the total number N of dents is almost 0 (zero), but when the melt amount V is 35 g, N becomes about 10 to 15 and when the melt amount V is 40 g. , N
Is about 50, and it is shown that N increases rapidly with an increase in the melt volume V.

The melt volume V will be described in more detail. For example, the condition of the melt amount V30g is GaAs
The diameter of the substrate is about 50 mm, and its area is about 19.6 cm ^2.
Therefore, 1.53 g / c per unit area of GaAs substrate
It corresponds to m ² . Similarly, the condition of the melt amount V20g is
This corresponds to 1.02 g / cm ² per unit area of the GaAs substrate, and the condition of the melt amount V40 g corresponds to 2.04 g / cm ² per unit area of the GaAs substrate.

Further, since the specific gravity of Ga is 5.9 g / cm ² , the volume of the growth chamber per unit area of these GaAs substrates is different with respect to the melt volume V of 20 g, 30 g and 40 g, respectively. 0.17cc / cm ² , 0.26c
c / cm ² and 0.35 cc / cm ² . Also, Ga
When the As substrates are arranged so as to face each other, it is natural that the required melt amount V per unit area of the GaAs substrate and the volume of the growth chamber are doubled.

Therefore, in order to reduce the number of dents,
From FIG. 6, it is desirable that the melt amount V is 35 g or less. Therefore, by calculation, the appropriate melt amount V per unit area of the GaAs substrate (growth substrate) is 1.79 g / cm ² or less, and the appropriate growth chamber volume is Is 0.3 cc / cm ² or less.

In FIG. 7, in the liquid phase epitaxial growth apparatus according to one embodiment of the present invention, the horizontal axis shows the total number N of dents (the number of thinly grown portions), and the vertical axis shows this. It is a figure which shows the correlation with the characteristic defect rate F (%) of the GaAs light emitting diode produced from the wafer. As is clear from FIG. 7, when the total number N of dents is about 3 to 15, the characteristic defect rate F is about 3 to 8 (%), but when the total number N is 20 or more. The characteristic defect rate F tends to increase rapidly.

In the liquid phase epitaxial growth method for a GaAs light emitting diode, since the peripheral portion of the wafer is ground and removed, the total number N of the dents is 3 to.
About 15 pieces corresponds to a value of the characteristic defect rate of the GaAs light emitting diode close to 0% for the wafer from which the peripheral portion is removed.

As a result of the liquid phase epitaxial growth apparatus according to the embodiment of the present invention shown in FIGS. 6 and 7, by setting the total number of dents N to be 3 to 15 or less, excellent liquid phase epitaxial growth can be achieved. A wafer can be obtained.

A liquid phase epitaxial growth apparatus according to an embodiment of the present invention in which the melt amount V per substrate is 30 g or less (our company's condition) will be described with reference to FIGS.

The general structure of a liquid phase epitaxial growth apparatus for mass production according to an embodiment of the present invention is shown in FIGS. FIG. 1 is an external perspective view of a liquid phase epitaxial growth apparatus of the present invention, FIGS. 2 to 4 are cross-sectional views of a liquid phase epitaxial growth apparatus before growth of the present invention, and FIG. 5 is a view of the present invention. It is a longitudinal cross-sectional view of the liquid phase epitaxial growth apparatus during growth.

In FIG. 1, a liquid phase epitaxial growth apparatus 10 comprises a growth boat storage member 13 for accommodating a growth boat 11 and an upper member 14 thereon, and an operating rod (rotation / movement) 12. . 15 is a melt drop port, 2
Reference numeral 5 is a melt leakage prevention ring, and 26 is a growth boat support portion.

2 to 5 are cross-sectional views of a mass production liquid phase epitaxial growth apparatus 10 according to an embodiment of the present invention. FIG. 2 shows a state before the growth (the melt is the melt of the upper member). FIG. 3 is a view showing a state during growth (a state at the time of injecting a melt), FIG. 4 is a view showing a state during growth, and FIG. FIG. 2 is a vertical sectional view taken along the line AA ′ of the liquid phase epitaxial growth apparatus 10 of the invention.

In FIG. 2, inside the growth boat 11, there is a growth chamber 21 composed of a growth GaAs substrate (III-V group semiconductor substrate, growth substrate) 20, a substrate holding plate 18, and the like. The melt injection port 11a is provided outside the growth boat 11.
And a convex joint portion 11b for rotation. The growth GaAs substrate 20 is held in close contact with the substrate holding plate 18. 12 is a control rod (rotation / movement), 1
2a is a concave joint for rotation between the operating rod and the growth boat 11, 13 is a growth boat storage member, 14 is an upper member, 15 is a melt drop port, 22 is a melt, and 23 is a melt reservoir. is there.

Furthermore, as a mechanism peculiar to the liquid phase epitaxial growth apparatus 10 for mass production according to one embodiment of the present invention, a melt leakage prevention ring 25 and a growth boat support portion 26 are provided. The melt drop port 15 is in close contact with the outer side wall surface of the growth boat 11, prevents the melt 22 from dropping into the space such as the growth chamber due to the surface tension of the melt such as Ga, and rotates. It is possible.

Next, the liquid phase epitaxial growth method of the present invention will be described with reference to FIGS. In FIG. 2, the growth GaAs substrate 20 is held in close contact with the substrate holding plate 18 and is held in the growth chamber 21. In the present invention, a plurality of sheets (50 to 10) are provided in one growth chamber.
0) GaAs substrates for growth 20 are provided for crystal growth. The melt 22 is the melt reservoir 23 of the upper member 14.
, The melt drop port 15 is a growth boat 11
Is closed by the outer side wall surface.

[Crystal Growth Procedure] (1) Substrate Setting Step The GaAs substrate 20 is arranged so that the back surface of the substrate holding plate 18 is in contact, and the growth boat 11 is assembled.

The entire growth boat 11 has a semi-cylindrical shape.
The substrate holding plate 1 is made up of parts, and grooves are formed on one side at regular intervals.
The GaAs substrate 20 for growth is set so that both surfaces 8 are aligned. After the setting is completed, the remaining one semi-cylindrical portion is covered, and both ends thereof are screwed with the caps to form the cylindrical growth boat 11. Further, the diameter of the growth chamber is made as close as possible to the diameter of the substrate excluding the holding portion (groove) so that crystal precipitation (precipitation of unnecessary crystal nuclei) does not occur outside the substrate.

According to the experiment, the dimensions (inner diameter) of the cross section of the growth chamber, than the outer diameter of the substrate surface in contact with the melt +0
It is desirable that the size is within about 5 mm. Ideally, it should be set to approximately 0 mm, but in reality, the size will be within +0 to 5 mm or so, but it is natural that this value is desirably small. When it is about +5 mm or more, unnecessary G is generated around the GaAs wafer.
It is not good because the aAs polycrystal is precipitated and its influence extends on the surface of the GaAs wafer.

(2) Pre-Growth Step After the melt leakage prevention ring 25, the growth boat support portion 26, etc. are set on the growth boat 11, these are housed in the growth boat storage member 13 and placed thereon. , Upper member 14
, Ga and GaAs polycrystal as raw materials, and Si for doping
Set the and in the melt reservoir 23 and operate the rod (rotation / movement) 12
Is set to the state shown in FIG. The liquid phase epitaxial growth apparatus 10 is loaded in a quartz tube in an electric furnace and placed in a hydrogen gas atmosphere. The electric furnace controlled to a predetermined temperature is heated to a high temperature (usually 900 to 1000 ° C.) and kept at the high temperature to sufficiently melt the raw material.

(3) Growth process In FIG. 2, when the operating rod 12 is moved to the left, the outer side wall surface of the growth boat 11 that has blocked the melt drop port 15 moves to the left, and the melt is melted. The melt injection port (melt passage) 11a is located below the drop port 15, and the melt 22 drops into the growth chamber 21 below, resulting in the state shown in FIG.

In FIG. 3, when the operating rod 12 is further moved to the left, the melt injection port (melt passage) 11a is closed by the melt leakage prevention ring 25 and the growth chamber 2
1 is filled with the melt 22. The growth boat 11 is provided with the growth boat support portion 26, is in a rotatable state, and is in the state of FIG.

In FIG. 4, the operating rod (rotation / movement) 12
The boat for growth 1 connected to the operating rod by rotating
1, while slowly rotating the temperature of the electric furnace,
The As crystal is grown on the surface of the GaAs substrate 20. At this time, the rotation speed of the growth boat 11 is about 0.5 to 2.0 rotations / minute.

3 and 4, 10 is a liquid phase epitaxial growth apparatus, 11 is a growth boat, 11a is a melt injection port, 12 is an operation rod (rotation / movement), 13 is a growth boat storage member, 14 is an upper member, 15 is a melt drop port, 1
Reference numeral 8 is a substrate holding plate, 20 is a growth GaAs substrate, 21 is a growth chamber, 22 is a melt, 23 is a melt reservoir, 25 is a melt leakage prevention ring, and 26 is a growth boat support portion. Thirty
Is the melt volume (melt volume per unit area V × 2) partitioned by the two growth GaAs substrates 20 and the inner wall surface of the growth boat 11.

FIG. 5 is a vertical sectional view of the liquid phase epitaxial growth apparatus 10 taken along the line AA 'in FIG. Figure 5
In FIG. 10, 10 is a liquid phase epitaxial growth apparatus, 11 is a growth boat, 11 a is a melt injection port (melt passage), 13
Is a boat storage member for growth, 14 is an upper member, 18 is a substrate holding plate, 20 is a GaAs substrate for growth, 22 is a melt, 2
3 is a melt reservoir.

As described above, in the liquid phase epitaxial growth apparatus 10 for mass production according to the embodiment of the present invention, as shown in FIGS. 1 to 5, the growth chamber 21 is partitioned by the substrate holding plate 18, The melt volume V that can exist therein is limited and controlled to the set melt volume V. Further, the growth melt amount 30 in each chamber can be optimized by the distance between the substrate holding plates 18 and the like according to the required growth layer thickness of the GaAs crystal, and the diameter of each growth chamber is outside the substrate to be grown. diameter and are almost over Itasu that structure, as explained above, according to the experiment, the dimensions (inner diameter) of the cross section of the growth chamber, than the outer diameter of the substrate surface in contact with the melt + 0 to 5 mm It is desirable that the size is equal to or less than that.

[0044]

As described above, according to the liquid phase epitaxial growth apparatus of the first aspect of the present invention, the upper member in which the melt reservoir for storing the melt of the crystal raw material is formed and the substrate are accommodated. A growth boat in which a growth chamber is formed, and in an electric furnace heated to a constant temperature, the melt stored in the melt reservoir is dropped into the growth chamber, and then the temperature is lowered. It is a liquid phase epitaxial growth apparatus for growing crystals on the surface, and the growth chamber formed in the growth boat is partitioned by a substrate holding plate into two or one substrates, and the growth substrate is used for holding the substrate. with the back surface plate is disposed in contact, with the melt is injected through the growth disposed the melt inlet to the boat to the growth chamber, melt in the growth chamber
The liquid leakage prevention ring is provided. Therefore, (1) by partitioning the growth chamber and optimizing the amount of melt for growth, the amount of GaAs crystals precipitated outside the substrate can be reduced, and an epitaxial wafer with a smooth wafer surface can be obtained.
By suppressing the abnormal growth of the wafer, it is possible to reduce the characteristic defect rate. (2) The material cost can be reduced by reducing the growth melt amount. According to the liquid phase epitaxial growth apparatus according to the embodiment of the present invention, the amount of raw material used can be covered by 30% of the conventional conditions (compared to our company).

Further, according to the liquid phase epitaxial growth apparatus according to the first aspect of the present invention, the dimensions of the cross section of said growth chamber (inner diameter), than the outer diameter of the substrate surface in contact with the melt, +
It is characterized in that the size is about 0 to 5 mm or less. Therefore, Ga on the outside of the substrate at the outer periphery of the growth chamber
Precipitation of As polycrystal can be prevented, generation of dents can be suppressed, and a high-quality GaAs epitaxial wafer can be obtained.

Further, according to the liquid phase epitaxial growth apparatus of the second aspect of the present invention, the volume of the growth chamber partitioned by the substrate holding plate is 0.3 cc / cm 3 per unit area of the growth substrate. It is characterized by being ² or less. Therefore, by controlling the volume of the growth chamber per unit area of the growth substrate, unnecessary GaAs crystal nuclei are prevented from being deposited and dents are prevented from being generated, and an epitaxial wafer with a smooth surface state and stable characteristics is obtained. Can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view of a liquid phase epitaxial growth apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a liquid phase epitaxial growth apparatus according to an embodiment of the present invention, showing a state before growth (a state when a melt is set in a melt reservoir of an upper member). Is.

FIG. 3 is a cross-sectional view of a liquid phase epitaxial growth apparatus according to an embodiment of the present invention, showing a state during growth (a state at the time of injecting a melt).

FIG. 4 is a transverse cross-sectional view of a liquid phase epitaxial growth apparatus according to an embodiment of the present invention, showing a state during growth.

FIG. 5 is a vertical sectional view taken along the line AA ′ in FIG. 3 of the liquid phase epitaxial growth apparatus 10 according to the embodiment of the present invention.

FIG. 6 shows a correlation between the melt amount V between the growth substrate and the growth substrate of the liquid phase epitaxial growth apparatus 10 according to one embodiment of the present invention and the total number N of the dents per batch. It is a figure.

FIG. 7 is a diagram showing a correlation N between the total number of dents in the liquid phase epitaxial growth apparatus 10 according to the embodiment of the present invention and a characteristic failure rate correlation of a GaAs light emitting diode made from a liquid phase epitaxial wafer. .

FIG. 8 is a perspective view of a conventional liquid phase epitaxial growth apparatus.

FIG. 9 is a cross-sectional view of a liquid phase epitaxial growth apparatus of a conventional example.

FIG. 10 is a cross-sectional view of a liquid phase epitaxial growth apparatus during growth of a conventional example.

FIG. 11 is a vertical cross-sectional view of a liquid phase epitaxial growth apparatus during growth of a conventional example.

[Explanation of symbols]

10 Liquid phase epitaxial growth system 11 growth boats 11a Melt inlet of growth boat (melt passage) 11b Growing boat joint 12 Operation rod (rotation / movement) 13 Growth boat storage member 14 Upper member 15 Melt drop port 16 rotor end 17 rotor bar 18 Board holding plate 19 rotor part 20 GaAs substrate for growth 21 Growth room 22 Melt 23 Melt pool 25 Melt leak prevention ring 26 Boat support for growth

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C30B 1/00-35/00

Claims (2)

(57) [Claims] 1. An electric furnace heated to a constant temperature, comprising an upper member having a melt reservoir for storing a melt of crystal raw material and a growth boat having a growth chamber for containing a substrate. In the liquid phase epitaxial growth apparatus for dropping the melt stored in the melt reservoir into the growth chamber, and then lowering the temperature to grow crystals on the substrate surface, the growth chamber formed in the growth boat Is divided into two or one substrates by a substrate holding plate, and the growth substrate is arranged such that the back surface of the substrate is in contact with the substrate holding plate and the melt is arranged in the growth boat. through the inlet into the growth chamber with the melt is injected, and arranged to melt the liquid leakage prevention ring growth chamber, the dimensions of the cross section of said growth chamber
The (inner diameter) is +0 from the outer diameter of the substrate surface in contact with the melt.
A liquid phase epitaxial growth apparatus having a size of about 5 mm or less . 2. The liquid phase epitaxial growth apparatus according to claim 1 , before being partitioned by the substrate holding plate.
The volume of the growth chamber is 0.3 c per unit area of the growth substrate.
A liquid phase epitaxial growth apparatus having a c / cm ² or less .