JPS60251194A - Process for growing single crystal of compound having high dissociation pressure - Google Patents

Abstract

PURPOSE:To enable precise control of thermal environment and to improve the quality of a single crystal of a compd. having high dissociation pressure by sensing the temp. of the surface of the melt optically through an optical window comprising a light transmittive material, and controlling a heating source basing on the sensed result. CONSTITUTION:GaAs is synthesized directly in a vessel contg. gaseous As sealed therein from Ga and As charged in a crucible 11. Then, a GaAs single crystal is pulled up. During this procedure, a tip of a quartz rod 1 for an optical window is held always at ca. 850 deg.C, and an clouding is caused on the rod. The indication of a two wavelength radiation pyrometer 2 shows maximally ca.+ or -5 deg.C variation influenced by the fluctuation of the temp. of the melt surface, but the mean value of the temp. after the pulling is commenced and the single crystal entering the straight barrel part, is held at + or -1 deg.C. As the result, a uniform crystal is obtd. The compd. having high dissociation pressure to be prepd. by this method is, for example, InAs, etc. in addition to the above descirbed GaAs.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to a method for producing single crystals of high dissociation pressure compounds, such as gallium arsenide substrates (Ga AS substrates), for ultrahigh speed ICs and lasers.

Conventional technology The Czochralski (CZ) method is a method for producing high dissociation pressure compounds such as Ga and As substrates for ultra-high speed ICs and lasers.
Compared to the B) method, it has the advantage of being able to easily obtain round ingots with a <100> orientation, and is therefore regarded as important. but,
This CZ method leaves unresolved problems in terms of optimization and controllability of crystal growth conditions for reducing and making the lattice defect density uniform in products.

One of these issues is optimizing the pressure of arsenic, which is a high dissociation pressure component, and the other is optimizing the thermal environment during growth.

To explain the first problem, conventionally, the mainstream was the liquid encapsulation Czochralski (LEC) method, which prevents arsenic from scattering by sealing the surface of the QaAs melt with boron oxide. Since it is not possible to make adjustments beyond the element distribution, more precise control of stoichiometry is required to further reduce the lattice defect density. To this end, during crystal growth, it is necessary to always cover the melt surface with a constant optimum arsenic pressure and control the stoichiometry of the melt.

For this purpose, it is necessary to seal the arsenic atmosphere in a container made of a material that is stable at the high temperatures of crystal growth, and this sealed container must also have an arsenic pressure control part to precisely control the arsenic pressure. It is necessary to have functions such as being able to seal in arsenic gas against rotation of the vertical axis, being able to easily cut off any number of marks to take out the crystal, and being able to optically observe the crystal during crystal growth. .

As a crystal growth device that satisfies these conditions, the present inventors have previously developed an arsenic compound single crystal growth device
No. 57883).

For the second problem, optimizing the thermal conditions during growth, it is important to control the temperature and temperature gradient at the growth interface. The temperature at the growth interface needs to be constant for precise control of stoichiometry, and the temperature gradient determines the growth rate, but thermal strain during solidification causes lattice defects. A constant defect density is necessary for crystal growth with uniform defect density.

Furthermore, lowering the temperature gradient at the solid-liquid interface has a great effect on lowering the dislocation density, but on the other hand, the range of appropriate melt temperature and pulling rate for crystal growth becomes narrower, and the precision of melt temperature cannot be adjusted. Without proper control, single crystal growth is impossible.

Conventionally, control of thermal conditions has been a blind spot in the CZ method. Conventionally, in order to compensate for the latent heat of solidification and maintain a constant temperature at the solid-liquid interface under conditions where the melt surface position decreases with crystal growth, the temperature of the heater must be determined empirically. Gradual changes have been made in accordance with established programs.

The problem that Ming is trying to decide.

However, the above method does not guarantee that the thermal environment at the solid-liquid interface remains constant, and is not sufficient to improve the quality of crystals.

It is effective to keep the melt surface position constant in order to control the thermal environment at the solid-liquid interface, but this alone may cause changes in the melt volume, crystal growth and the release of latent heat associated with it, and the crucible. The melt surface temperature cannot be kept constant due to changes in the end position.

For this reason, it is necessary to directly detect and control the humidity at the surface of the melt. The first possible way to do this is to use a thermocouple, but inserting a thermocouple directly into the melt will cause unnecessary disturbance to the movement of the melt as the crucible rotates, which will hinder crystal growth. Give uniformity factor. Moreover, it is difficult to read the temperature in areas with strong temperature gradients, and it is also difficult to operate.

Means for Solving the Problems This invention attempts to solve the difficulty of precisely controlling the thermal environment of the C7 method, and its structure is to seal the high dissociation pressure component gas and reduce the pressure. In a method of pulling a single crystal of a high dissociation pressure compound in a controlled manner, the temperature of the melt surface is optically detected through an optical window made of a translucent material that is tightly bonded to the inner container that seals the gas;
This is a high dissociation pressure compound single crystal growth method characterized by controlling the heating source based on the results.

In the method described in Japanese Patent Application No. 58-157883, the arsenic compound single crystal is grown in a container that seals arsenic gas, so there is no need for sealing with boron oxide, which was conventionally required, and it is not necessary to use a sealed container. The melt surface can be directly observed using a penetrating optical window such as a quartz rod, quartz pipe, or glass fiber. This optical window may be made of other light-transmitting material, such as sapphire, and may also have a plate-like shape provided in the inner container. The joint with the inner container must be able to seal the arsenic atmosphere sufficiently well, and examples of joints used for this purpose include the use of a taper joint and a solid gasket such as thermally expandable graphite.

Through such an optical window, the temperature of the melt surface can be measured using an infrared radiation thermometer. At this time, Ga is applied to the optical window.
203, GaAs.

When condensation of As or the like occurs, light absorption occurs and significantly impedes measurement, but this can be avoided by the following method.

1) Temperature at the tip of the optical window, 610-950℃ or 1
Maintain the temperature between 080 and 1200°C.

2) Do not use quartz as the arsenic atmosphere sealed container or crucible material, reduce residual oxygen, and use Qa203 or GaAS.
To suppress reactions caused by oxygen that cause condensation.

3) By setting the wavelength used for the infrared radiation thermometer to around 1 μm and using a three-wavelength type, constant temperature support can be obtained even when cloudy weather occurs.

Arsenic gas and quartz do not absorb light in this wavelength range, and are suitable for the purpose of this invention.

Embodiments of the present invention will be specifically described with reference to the drawings. FIG. 1 is a sectional view showing an outline of an apparatus suitable for carrying out the present invention.

An inner chamber 10 having an inner chamber lid 9 inside an outer chamber 15 having an inert gas introduction pipe 13 and an exhaust pipe 14.
A heater 5 and a main heater 6 are provided to surround the inner chamber. Inside the inner chamber 10, there is a PB supported by a rotating shaft that penetrates the walls of the outer chamber 15 and the inner chamber 10, can move up and down, and can rotate.
There is a crucible 11 made of N, and an upper shaft 16 for pulling up a single crystal 12 from a raw material melt in the crucible passes through an outer chamber 15 and an inner chamber lid 9, and can move up and down and rotate. A seal 7 is provided at a location where the rotating shaft passes through the inner chamber 10 and the inner chamber lid 9, and the inner chamber lid 9 is provided with an arsenic pressure controlled furnace 4.

A quartz rod 1 is provided as an optical window passing through the outer chamber 15 and the inner chamber lid 9. A tapered joint 17 was used to join the inner chamber lid. A three-wavelength infrared radiation pyrometer 2 using wavelengths of 1 μm and 0.85 μm is used as a thermometer to detect the temperature of the melt surface in the crucible 11 through this.

Using the analog signal obtained from the three-wavelength infrared radiation pyrometer 2 and the electromotive force of the thermocouple 8 in contact with the main heater 6 for heating the crucible, the output of the heater is controlled in a cascade manner by the cascade temperature controller 3. Control. In addition, in order to maintain the melt level in the crucible 11 at a constant height while the single crystal 12 is being pulled, a drop in the liquid level is detected based on a signal from a gravimetric automatic diameter control sensor connected to the pulling rotation shaft. is determined by a computer and automatically corrected.

In the above embodiment, the optical window 1 is joined by the taper joint 17, but as shown in FIG. This may also be done by pressing down. Such a mechanism may be provided at a penetration point of the outer chamber 15.

Load a total of 800g of Ga and As into Ruppo 11,
After directly synthesizing GaAs in an arsenic gas-sealed container, G
a As single crystal was pulled up.

During this time, the tip of the quartz rod 1 for optical window is always kept at about 850°C.
cloudiness did not occur.

The indication from the dual-wavelength radiation pyrometer 2 reflected fluctuations in the temperature of the liquid surface, and showed a fluctuation of approximately ±5°C at its peak value. Average value is ± 1
It was kept at ℃.

As a result, a uniform crystal (diameter 4.5 cmφ, length 7cI11) with a central diameter of 2.5 cmφ (EPD2ooocI11-3 or less) was obtained from the front part to the back part.

Although the present invention has been explained using GaAs as an example, it is not limited to Ga AS, and can also be applied to high dissociation pressure compounds such as InAS.

As explained above, according to the present invention, it is possible to produce a high dissociation pressure compound single crystal in which the longitudinal uniformity of dislocation distribution is greatly improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of an apparatus suitable for carrying out the present invention, and FIG. 2 is a detailed view of another embodiment of the joint portion of the optical window with the inner container. DESCRIPTION OF SYMBOLS 1... Quartz rond, 2... Two-wave infrared radiation pyrometer, 3... Cascade temperature controller, 4... Arsenic pressure control furnace, 5... Heater, 6... Main heater , 7... Seal, 8... Thermocouple, 9...
Inner chamber lid, 10... Inner chamber, 11...
Crucible, 12... Single crystal, 13... Inert gas introduction pipe, 14... Exhaust pipe, 15... Outer chamber, 16
... Pulling shaft, 11 ... Taper joint, 18 ... Solid gasket, 19 ... Screw, Patent applicant New Technology Development Corporation (2 others) Agent Patent attorney Hidetake Komatsu ↑ 2 Diagram procedure Neho Seisho (spontaneous) Manabu Shiga, Director General of the Patent Office 1, Indication of the case Patent Application No. 104439 of 1982 2
, Title of the invention Method for growing single crystals of high dissociation pressure compounds 3 Relationship with the case of the person making the amendment Name of the patent applicant New Technology Development Corporation (2 idiots) 7 Contents of the amendment (1) Specification page 7 Correct “thermal extensibility” in the second line to “expansion”. (2) "Thermal expandability" on page 9, line 18 is corrected to "expansion." (3) In the first line of page 10, "such a mechanism" is corrected to "such a rolling down mechanism". 4) “1 sticker” on page 11, line 14 is “rotating sticker”
I am corrected.

Claims (1)

[Scope of Claims] (1) In a method for pulling a single crystal of a high dissociation pressure compound while sealing a high dissociation pressure component gas and controlling the pressure, the component gas is tightly bonded to an inner container that seals the gas. A high dissociation pressure compound single crystal growth method characterized by optically detecting the temperature of the melt surface through an optical window made of a translucent material and controlling the heating source based on the result. (2) Optical window A method for growing a single crystal of a high dissociation pressure compound according to claim (1), in which the optical window is joined to the inner container with a tapered joint. (3) A patent claim, in which the optical window is joined to the inner container using a solid gasket. A method for growing a single crystal of a high dissociation pressure compound according to scope (1).