JPH0751479B2 - Single crystal growth method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a technique for growing InP single crystals, and in particular, an InP single crystal doped with sulfur or zinc is referred to as a liquid-encapsulated Czochralski method (hereinafter referred to as LEC method). ) Related to technology that is effective when used for manufacturing.

[Prior Art] One of the methods for growing InP single crystals is the LEC method. I according to LEC method
When growing an nP single crystal, if the temperature gradient is small, the surface temperature of the liquid encapsulant becomes too high and the surface of the single crystal exposed on the encapsulant during crystal pull-up decomposes, and it does not melt or dissolve. It will not be possible to raise the price. Therefore, in the growth of InP single crystal by LEC method, it was necessary to increase the temperature gradient in the crystal axis direction. However, on the contrary, if the temperature gradient is too large, the thermal stress in the crystal becomes large and the EPD (dislocation density) increases.

As described above, in the growth of InP single crystals by the conventional LEC method, it was not possible to simultaneously achieve the requirements for both single crystallization and low EPD by controlling the temperature gradient.

In order to solve such a problem, various techniques such as the VM-FEC method, the direct synthesis method and the vapor pressure control method have been proposed (for example, JP-A-63-274690).

[Problems to be Solved by the Invention] All of the above conventional techniques have problems in practical use. The reason is that the VM-FEC method and the direct synthesis method have a low single crystallization rate and a low yield. Further, in the vapor pressure control method, in order to make the container a high pressure, it is necessary to make the container a tightly sealed structure by sealing the pulling shaft and the crucible rotation shaft with a sealant, which makes the device and work complicated, This is because it is necessary to destroy a part of the closed container each time it grows.

Further, in the InP single crystal containing sulfur or zinc, it is possible to lower the dislocation density by utilizing the impurity hardening effect. However, the average EPD in a 2 inch diameter InP single crystal
Carrier concentration of 6 to 7 x 10 to keep the value below 500 cm ^-2.
Dopant (impurity) must be implanted until it becomes more than ¹⁹ cm ^-3 . In such a single crystal having a high carrier concentration, if the epitaxial growth is performed on the substrate when manufacturing the device, the problem that the dopant in the crystal diffuses into the epitaxial layer and the resistivity changes Occurs.

The present invention has been made to solve the above problems, and an object of the present invention is to use a relatively simple device and further to destroy a part of the device or increase the amount of dopant. It is an object of the present invention to provide a crystal production technique capable of industrially producing an S- or Zn-containing InP single crystal having a low dislocation density and a high single crystallization rate.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention, in growing an InP single crystal containing sulfur or zinc by the LEC method, penetrates at least the crystal pulling axis around the crucible. The part is covered with a semi-enclosed container in which a cylindrical portion that fits with the pulling shaft is formed, and the ratio A / L of the cross-sectional area A of the gap between the cylindrical portion and the pulling shaft and the length L of the cylindrical portion is 0.0
Set to 6 cm or less, the semi-enclosed container is connected to a vapor replenishing means for replenishing the reduced amount of the vapor of the volatile element flowing out from the gap of the pulling shaft, and the semi-enclosed vessel in the semi-closed vessel Phosphorus vapor pressure of 0.01atm or more and 4atm or less, and the vertical temperature gradient of the liquid sealant is 50 ℃ / cm or more.
The crystal was pulled up by controlling at 0 ° C./cm or less.

Here, the temperature gradient is a value obtained by dividing the temperature difference between the melt interface and the surface of the sealant by the thickness of the sealant.

[Operation] According to the above-described means, it is possible to prevent the vaporization of phosphorus having a high vapor pressure from the surface of the single crystal exposed on the sealant by the phosphorus vapor pressure applied in the semi-enclosed container,
Since the temperature gradient is not too low, melting of the surface of the single crystal and generation of twins can be prevented, and the growth of dislocations can be suppressed because the temperature gradient is not too high, resulting in a low dislocation density and a single crystallization rate. High S or Zn-containing InP single crystals can be produced.

Moreover, since the phosphorus vapor pressure was set to 4 atm or less, a structure having a cylindrical portion that fits the pulling shaft at the portion where the pulling shaft penetrates is simple and uses a semi-hermetic container that can be removed without breaking.
It becomes possible to grow an InP single crystal, and it becomes easy to commercialize it industrially.

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

[Embodiment] FIG. 1 shows an embodiment of a single crystal growth apparatus used for carrying out the method of the present invention.

In FIG. 1, 1 is a high-pressure container pressurized by an inert gas or nitrogen gas, 2 is a crucible which is arranged in the center of the high-pressure container 1 and is supported by a rotating shaft 3, and a raw material (InP Polycrystalline block) and sealant 4 such as B ₂ O ₃
Is stored. Further, from above the high-pressure container 1, a pull-up shaft 5 is rotatably and vertically movable toward the inside of the crucible 2.

In this embodiment, a cover member 6 is provided around the crucible 2 and a heating heater 7 is arranged outside the cover member 6. On the bottom wall of the cover member 6, a cylindrical portion 6a that fits with the rotating shaft 3 that supports the crucible is formed. A cover member 8 is attached to the upper portion of the cover member 6, and the cover member 6 and the cover member 8 constitute a semi-hermetic container. A heat retaining heater is arranged around the cover member 8, and a cylindrical portion 8a that fits the pulling shaft 5 is formed at the upper end of the cover member 8.

In this embodiment, the gap between the cylindrical portion 8a and the pulling shaft 5 and the gap between the rotating shaft 3 and the cylindrical portion 6a are the ratio A / of the sectional area A of the gap and the length L of the cylindrical portions 6a, 8a. It is designed so that each L is 0.06 cm or less.

Further, in the device of this embodiment, a conduit 6b having a closed lower end is extended downward from a part of the bottom wall of the cover member 6, and an auxiliary heater 10 is arranged around the lower portion of the conduit 6b. ing. A volatile element such as arsenic is put into the conduit 6b and heated by the auxiliary heater 10, so that an appropriate amount of the vapor is placed in a space for forming a crystal growth atmosphere defined by the cover member 6 and the cover member 8. It is ready to supply. That is, a part of the conduit 6b and the auxiliary heater 10 form a reservoir as a vapor replenishing means.

By adjusting the temperature of the heater 10 which constitutes this reservoir, it is possible to generate and compensate the amount of vapor corresponding to the amount of phosphorus vapor flowing out from the gap between the pulling shaft 5 and the rotating shaft 3. As a result, the phosphorus vapor pressure around the crucible 2 can be kept constant during the crystal growth for a long time (+ several hours).

In this way, if the vapor pressure of phosphorus is kept constant, it is possible to prevent the volatilization of phosphorus from the surfaces of the raw material melt 16 and the growing crystal 17 in the crucible as much as possible. In addition, the apparatus of this embodiment has a simple structure, avoids the close contact between the shaft and the container, which is a problem in the double melt sealing method, and allows the apparatus to be used repeatedly, resulting in a dramatic increase in productivity. In addition, the contamination due to the dropping of the sealing material from the melt sealing portion is prevented, and a high-quality single crystal can be manufactured with good reproducibility.

Next, using the single crystal pulling apparatus shown in FIG.
A procedure for growing an InP single crystal will be described.

First, 2300 g of InP polycrystal synthesized by HB method as a raw material
And 0.8 g of In ₂ S ₃ as an additive are charged in the crucible,
On top of that, 700 g of B ₂ C ₃ was added as a sealant. The crucible used is made of quartz glass and has an inner diameter of 6 inches.
Further, the temperature gradient in B ₂ O ₃ was set to 75 ° C./cm, the inside of the high-pressure vessel 1 was filled with 40 atm of N ₂ gas, and the vapor pressure of phosphorus supplied by the reservoir was set to 0.1 atm. Then, the pulling shaft 5 is rotated at a speed of 10 rpm, and the rotating shaft 3 of the crucible 2 is rotated at 3 rpm.
While rotating in the opposite direction to the pulling shaft at a speed of 0 rpm, 10 mm
The pulling shaft 5 was raised at a speed of / hr, and the crystal was grown for about 12 hours.

As a result, the diameter of the straight body part is 60 mm, the length is 150 mm, and the weight is about 2.0 kg.
Inp single crystal was obtained. The surface of the crystals had a metallic luster, indicating no decomposition of phosphorus. Crystals grown in an open system without semi-sealing the container without controlling the vapor pressure have large surface decomposition, and when the wafer is cut out by cutting perpendicular to the growth direction, In droplets due to decomposition are seen in the peripheral part. However, no In droplet was generated in the crystal grown by controlling the vapor pressure in the above example.

The S-doped InP crystal obtained as described above was cut in the direction orthogonal to the pulling axis, and the carrier concentration and dislocation density were measured.

FIG. 2 shows the relationship between the EPD and the carrier concentration, and for comparison, the results of crystals pulled by the conventional LEC method are also shown. In the figure, ◆ indicates a temperature gradient of 120 to 150 ° C / cm.
A plot of EPD values measured for the InP single crystal grown by the conventional general LEC method.
The mark is a plot of the EPD value measured for the InP single crystal obtained by applying the method of the present invention. As can be seen from Fig. 2, low EPD even with lower carrier concentration than before.
You can see that it has been made.

Fig. 3 shows the EPD distribution at a carrier concentration of 6.0 × 10 ¹⁹ cm ^-3 . Of these, FIG. 7A relates to a crystal grown by the conventional LEC method, and FIG. 3B relates to a crystal grown in this example. In the figure, □ is the average E in a square area with a side of 5 mm.
Area where PD value is less than 500cm ^-2 , Is an area where the EPD value is 500 to 5000 cm ^-2 or less, Indicates that the EPD value is in the region exceeding 5000 cm ^-2 . From the figure, in this example, there is a dislocation-free region with a dislocation density of 500 / cm ² or less of 40 mmφ or more, but with the conventional method, it is 20 mmφ.
It turns out that it is a degree.

Although the temperature gradient in the encapsulant was set to 75 ° C./cm in the above example, the present invention is not limited to this. However, if the temperature gradient is 90 ° C / cm or more, the dislocation-free region becomes narrower, and
If the temperature is less than ℃ / cm, twinning is likely to occur.
The range of ° C / cm is appropriate.

Further, in the above-mentioned embodiment, the production of the InP single crystal doped with sulfur has been described, but the present invention can be applied to the production of an InP single crystal containing zinc and the same effect can be obtained.

[Effects of the Invention] As described above, according to the present invention, in growing an InP single crystal containing sulfur or zinc, at least a portion through which the crystal pulling shaft penetrates is formed with a cylindrical portion fitted with the pulling shaft. While covering the circumference of the crucible with a closed container, set the ratio A / L of the clearance cross-sectional area A between the cylindrical part and the pulling shaft and the length L of the cylindrical part to 0.06 cm or less. , Connecting a vapor replenishing means for replenishing the reduced amount of vapor of the volatile element flowing out from the gap of the pulling shaft, and 0.01 atm or more 4 atm in the semi-sealed container by the vapor replenishing means.
Since phosphorus vapor pressure of m or less is applied and the vertical temperature gradient of the liquid sealant is controlled to 50 ° C / cm or more and 90 ° C / cm or less to pull up the crystal, it is applied to the semi-sealed container. Phosphorus vapor pressure can prevent phosphorus from evaporating from the surface of the single crystal exposed on the encapsulant, and can prevent melting of the surface of the single crystal and generation of twins because the temperature gradient is not too low. Since the temperature gradient is not too high, dislocation multiplication can be suppressed, so that an S or Zn-containing InP single crystal having a low dislocation density and a high single crystallization rate can be manufactured.

Moreover, since the phosphorus vapor pressure was set to 4 atm or less, a structure having a cylindrical portion that fits with the pulling shaft at the portion where the pulling shaft penetrates is simple and a semi-sealed container that can be removed without breaking the InP single crystal Therefore, there is an effect that it can be cultivated and it becomes easy to put into practical use industrially.

In the above embodiment, cylindrical portions 6a, 8a having a ratio A / L of the clearance cross-sectional area A and the length L of not more than a predetermined value are provided around both the rotating shaft 3 supporting the crucible and the pulling shaft 5. Although provided,
Since the container can be opened and closed by providing at least the pulling shaft 5 with such a structure, the rotating shaft 3 can be sealed with a sealing agent such as B ₂ O ₃ .
There is no problem in practical use.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a single crystal growth apparatus used in the method of the present invention, and FIG. 2 is a relation between dislocation density and carrier concentration of crystals grown by the method of the present invention and a conventional method, respectively. 3 (A) and 3 (B) are EPD maps showing dislocation density distributions in the wafer plane of crystals grown by the conventional method and the method of the present invention, respectively. 1 ... High-pressure container, 2 ... Crucible, 3 ... Rotating shaft, 5 ...
Lifting shaft, 6,8 ... Semi-closed container, 7 ... Heater, 6a, 8a
...... Cylindrical part, 6b, 10 ...... Steam supply means (reservoir).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Osamu Oda Inventor Osamu 3-17-35, Niizominami, Toda City, Saitama Prefecture, Japan Mining Co., Ltd. Electronic Materials and Parts Research Laboratories (56) References JP-A-60-11299 (JP, A)

Claims (2)

[Claims] 1. A raw material, an additive, and a sealant are placed in a crucible and heated and melted by a heater, and a seed crystal is brought into contact with the surface of the raw material melt covered with a liquid sealant, and this is gradually added. In growing an InP single crystal containing sulfur or zinc by pulling up, around the periphery of the crucible, a semi-hermetic container in which at least a portion where the crystal pulling shaft penetrates is formed with a cylindrical portion that fits with the pulling shaft. Along with covering, the ratio A / L of the gap cross-sectional area A between the cylindrical portion and the pulling shaft and the length L of the cylindrical portion is set to 0.06 cm or less, and the semi-hermetic container flows out from the gap between the pulling shafts. The vapor replenishment means for replenishing the reduced amount of the vapor of the volatile element is connected, and by the vapor replenishment means, 0.01 atm or more and 4 atm in the semi-enclosed container.
A method for growing a single crystal, which comprises pulling a crystal by applying the following phosphorus vapor pressure and controlling a vertical temperature gradient of the liquid sealant to 50 ° C./cm or more and 90 ° C./cm or less. 2. The steam supply means comprises a bottomed cylindrical conduit connected to the lower part of the semi-enclosed container and a heater provided around the conduit, and the temperature of the heater is adjusted to adjust the temperature. 2. The single crystal growth method according to claim 1, wherein phosphorus vapor is supplied in an amount commensurate with the amount of volatile element vapor flowing out from the gap between the pulling shafts.