JPH0699234B2 - Compound semiconductor single crystal growth equipment - Google Patents

Description

The present invention relates to a single crystal growth apparatus for growing a III-V group compound semiconductor crystal such as GaAs, InP or the like into a single crystal by using the liquid sealed Czochralski method. is there.

[Conventional technology]

Conventionally, this type of compound semiconductor single crystal growth method has been performed using a growth apparatus as shown in FIG. That is, the semiconductor raw material and B ₂ O ₃ , which is a sealant, are put into the crucible 15 installed on the susceptor 14 and heated by the heater 13 to be in a molten state. FIG. 2 shows the sealing B ₂ O ₃ 10 and the melt 11 in a molten state. At this time, the inside of the container 18 is pressurized by the inert gas. Next, the seed crystal 8 attached to the seed crystal holder 6 is lowered and brought into contact with the melt 11, and then the crucible temperature is lowered to bring the melt 11 into a supersaturated state and the seed crystal 8
Is pulled up to grow a crystal 9.

[Problems to be solved by the invention]

In the conventional technique of growing a compound semiconductor single crystal by the liquid-encapsulated Czochralski method, the atmosphere between the graphite heater 13 and the heat insulating material 12 and the encapsulating B ₂ O ₃ 10 shown in FIG. Gas can move freely by heat convection.
As a result, carbon dioxide gas generated from the graphite member is reduced by B ₂ O ₃ , and the reduced carbon is mixed into the growing crystal, and the carbon dioxide is approximately 5 × 10 ¹⁵ cm ⁻³ to 1 × 10 ¹⁶ cm ^−3.
A low concentration of acceptor impurity level is formed, and the electrical characteristics of the grown crystal after high temperature heat treatment are unstable, or V
There are drawbacks such that the deviation of the composition ratio of the group III / III element has a large influence on the electrical characteristics, and the activation rate after Si ion implantation in the LSI manufacturing process is low.

The object of the present invention is to eliminate such drawbacks and to prevent the atmospheric gas from moving back and forth by disposing a quartz inner tube inside thereof, thereby eliminating the incorporation of carbon into the crystal and stabilizing the electrical characteristics of the crystal. Another object of the present invention is to provide a compound semiconductor single crystal growth apparatus.

[Means for solving problems]

According to the constitution of the present invention, the compound semiconductor material in the crucible is heated by the heater to form a melt, and the surface of the melt is melted with B ₂ O _{3 of the} liquid sealant.
In a compound semiconductor single crystal growth apparatus using a liquid-sealed Czochralski method for growing a compound semiconductor single crystal while covering with a lower container made of a heat-resistant material that accommodates the crucible separately from the heater and does not react with atmospheric gas. An upper container having a lower end that is made of the same material as the lower container and that has a rubbing structure with its upper end, and has an insert portion for the crystal pulling shaft at the upper end and further has an inert gas supply end and an output end The crucible is inserted into the upper container and the lower container and sealed in the inert gas.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a vertical sectional view showing a compound semiconductor single crystal growth apparatus according to an embodiment of the present invention.

The apparatus of this embodiment has a lower inner tube 5 made of quartz capable of holding a PBN crucible 15, and has a hole larger than the outer diameter of the seed crystal holder 6 in the center of the upper end of the upper inner tube 1, and It has a saucer-like structure that can seal between the seed crystal holders 6 of the upper inner tube 1 with a sealing B ₂ O ₃ in order to prevent the atmospheric gas inside and outside the inner tube from entering and leaving at high temperature. . The upper inner pipe 1 and the lower inner pipe 5 have an inner pipe having a structure in which an airtightness is maintained by a laminating structure, and an inert gas introducing port 2 and a valve 4 for releasing the pressure inside the inner pipe to the outside are provided.

An example of growing an undoped GaAs crystal will be described.

This crystal growth method can be applied to other III-V group compound semiconductors such as InP, GaP, and InAs, regardless of whether they are undoped or impurity-doped.

Raw materials Ga and As (or polycrystalline GaAs) are put into the PBN crucible 15, and further B ₂ O ₃ (10) which is a sealant is put therein. Crucible 15
The lower inner pipe 5 is housed in the susceptor 14 for mechanically holding the crucible 15, and then the crucible 15 containing the raw material is arranged. Then, the upper inner pipe 1 is rubbed with the lower inner pipe 5, and the gas introduction pipe 2 B ₂ for connecting the seed crystal holder 6 and the upper inner tube 1 by connecting the inert gas inlet made of Mo etc.
Place O ₃ on the upper end of the upper inner tube 1.

For gas replacement with an inert gas after the growth furnace is closed, vacuum exhaust is performed from the gap between the upper end of the upper inner tube 1 and the seed crystal holder 6, and gas is introduced from the inert gas inlet and pressurized. By.

After the gas replacement in the growth furnace is completed, the inside of the furnace is heated to a high pressure and the temperature is raised. In this temperature rising process, it is not a problem that the crucible 15 is covered with the inner quartz tube. Next, after raising the temperature, it is necessary to reduce the pressure to about 2 atm in order to remove the bubbles melted in the sealant B ₂ O ₃ . At this time, the valve 4 attached to the upper inner tube 1 allows the atmospheric gas in the inner tube to escape through the inside of the growth furnace to the outside of the growth furnace.

Next, the inside of the inner tube was pressurized again to perform seeding and growth. As a result, the carbon concentration in the grown crystal was about 2 × 10 ¹⁵ cm.
It was reduced to ^-3 .

On the other hand, in the conventional compound semiconductor growth method shown in FIG. 2, the graphite members such as the heat insulating material 12, the heater 13, the susceptor 14 and the sealant B ₂ O ₃ 10 share the atmospheric gas. As a result, carbon of a concentration of about 5 × 10 ¹⁵ cm ^-3 was mixed in the GaAs crystal grown by reducing carbon dioxide in the atmosphere gas with B ₂ O ₃ .

Next, another example of the compound semiconductor single crystal growth method of the present invention will be described.

Silicon and silicon oxide, which are scattered from the inner tube of quartz for a long time at high temperature into the atmosphere gas, react with B ₂ O ₃ as in the case of carbon dioxide gas, and as a result, they are mixed in the grown crystal and become shallow donors. Form a rank and do not become semi-insulating.

Therefore, by setting the pressure to a low pressure (5 atm) so that convection of the atmospheric gas does not occur so much, and thickening B ₂ O ₃ (usually about 2 cm to 6 cm), about 1 × 10 ⁷ Ω ・We were able to grow cm semi-insulating GaAs crystals.

The As that is scattered during the direct synthesis of GaAs adheres to the inner wall of the quartz inner tube, serves as a kind of coating, and suppresses the scattering of silicon and silicon oxide from the quartz inner tube.
It is considered that this contributes to the semi-insulating property.

As described above, the present invention can be applied to growth of a semi-insulating substrate.

〔The invention's effect〕

As described above, according to the present invention, the crucible, the compound semiconductor melt, the sealant B ₂ O ₃ and the graphite member such as the heater and the heat insulating material do not share the atmospheric gas.
By arranging the inner tube made of quartz or the like, there is an effect that the concentration of carbon mixed in the grown crystal can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of an embodiment of a compound semiconductor single crystal growth apparatus of the present invention, and FIG. 2 is a vertical sectional view of a crystal growth apparatus for explaining an example of a conventional compound semiconductor growth method. It is a figure. 1 ... upper quartz inner tube, 2 ... inert gas inlet pipe, 3 ... for sealing between the upper quartz inner tube and the seed crystal holder B ₂ O _3, 4 ... bulb, 5 ... lower quartz inner tube, 6 ... Seed crystal holder, 7 ... Upper axis, 8 ... Seed crystal, 9 ... Crystal, 10 ... Sealing B ₂ O ₃ , 11 ... Melt solution, 12 ... Heat insulating material, 13 ... Heater, 14 ... Susceptor, 15 ... Crucible, 16 ... Pedestal, 17 ... Lower shaft, 18 ... Container.

Claims (1)

[Claims] 1. A liquid-sealed Czochralski that grows a compound semiconductor single crystal while heating a compound semiconductor material in a crucible with a heater to form a melt and covering the surface of the melt with B ₂ O ₃ as a liquid sealant. In the compound semiconductor single crystal growth apparatus using the method, a lower container made of a heat-resistant material that accommodates the crucible separately from the heater and does not react with atmospheric gas,
An upper container having a lower end having a rubbing structure made of the same material as that of the lower container and having an insert portion of the crystal pulling shaft at the upper end and further having an inert gas supply end and an output end is provided, A compound semiconductor single crystal growth apparatus, wherein the crucible is inserted into the upper container and the lower container so as to be sealed in the inert gas.