JPS59111994A - How to grow crystals - Google Patents

Abstract

PURPOSE:To extrude the influence of heat convection and turbulent flow and to grow crystal with low oxygen concentration, by providing the inside of a crucible to put melt in it with the second crucible for growing crystal having a sh allow bottom and holes on the side face. CONSTITUTION:The inside of the crucible 1 to put the Si melt 12 in it is provided with the crucible 9 made of the same material having a shallow bottom and the plural through holes 10 on the side face in such a way that it is hung by the Mo wire 11 and fixed to the center of the crucible 1. The melt 12 is introduced through the holes 10 to the crucible 9, the tip of a seed crystal is brought into contact with the melt 12 in the crucible 9, and the grown crystal 4 is pulled up. A carbon heater to heat and to melt a semiconductor material for growth and to maintain a molten state is set at the outer periphery of the crucible 1. Consequently, a tubulent flow occuring from the bottom of the crucible 1 is cut off, heat convection reaches the liquid level, the Si melt which has released oxygen with high concentration in the form of SiO2 is introduced from the holes 10 to the crucible 9. Since the crucible 9 has the shallow bottom, and heat convection will not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for growing crystals in which the effects of turbulence and thermal convection in a melt are blocked.

(bl Technology background IC,) Semiconductor elements such as transistors are silicon (Si)
), potassium arsenide (QaAs), etc., but these crystals are formed using the Czochralski method (abbreviated as CZ) or the floating zone method (abbreviated as F).
Here, the C2 method is characterized by the ability to make the diameter large, and the F'Z method is characterized by the fact that it is easy to obtain high-purity products. For the purpose of mass producing semiconductor devices, crystals obtained by the C2 method are often used.

(C) Prior art and problems In the C2 method, a polycrystalline body made of the same material as the single crystal to be grown is placed in a crucible, heated and melted in an inert gas, and the growing melt is brought into contact with a seed crystal. By gradually pulling up the crystal while maintaining an equilibrium state, a single crystal is grown using the 9-seed crystal as a nucleus.

In mass-produced semiconductor devices such as ICs and transistors, the diameter of the crystal substrate (wafer) used for production is increasingly becoming dog-shaped from the viewpoint of equalizing characteristics and reducing costs.

For example, for Si, the diameter is 4 [inches] and the length is 1 [W].
These are common, and those with a diameter of 5 inches are also being made. In this way, as the diameter of the grown crystal becomes larger and longer, the crucible used also becomes larger in proportion. For example, the dimensions of a quartz (Si02) crucible used for Si crystals with a diameter of 4 to 5 [inches] are approximately 300 [mm] in diameter and 200 cm in height, and approximately 2o (ky:). High-purity polycrystalline Si is placed in the crucible and heated and melted into a melt using a carbon heater (not shown) placed around the crucible.As the crucible becomes larger, the convection of the melt becomes more pronounced. However, this effect appears in pulled crystals.Hereinafter, Si, which is currently the largest crystal pulled, will be explained as an example.

Figure 1 is a cross-sectional view of the essential parts of the crucible and the growing crystal when Si single crystal is being pulled by the CZ method.
The crucible 1 containing the i-body is heated in an argon (Ar) atmosphere by energizing a carbon heater (not shown) provided surrounding it, and the polycrystalline Si body is melted into a melt 2. ing. Here, the melting point of 81 is 1410
[°C], so it is necessary to heat it above this temperature to maintain the melt state.

Next, for crystal growth, the tip of the seed crystal is fixed to the tip of the pulling shaft 3 and immersed in the melt 2, and while maintaining an equilibrium state, the seed crystal is gradually pulled up to grow a straight body. Growth of crystal 4 takes place. However, the diameter of crucible 1 is approximately 3 o C
Under the conditions that the depth is about 200 [rn voice] and the temperature of the melt in this exceeds 14.00 [:'C:], the temperature of the melt 2 at the bottom of the crucible is equal to that at the surface. Comparative number 10
['C:] High heat convection 5 is occurring due to kneading.

That is, thermal convection occurs from the bottom of the five-piece crucible 1 along the inner wall and circulates around the growing single crystal. Here, in order to scrape the inner wall of the crucible 1 made of five-quartz quartz, 5ho2, which is a component of the crucible, is dissolved into the melt 2.
Increase the oxygen concentration in the melt 2. Therefore, the oxygen concentration in the growing crystal 4 is increased. Therefore, conventionally, the growing crystal 4 itself and the crucible 1 are rotated in opposite directions for the purpose of alleviating the influence of thermal convection 5 on crystal quality. The melt 2 interferes with the thermal convection 5 in the horizontal forces 6 caused by the rotation of the crucible 1, causing rough fluctuations in the melt 2, which causes a different impurity concentration distribution in the growing crystal 4. Prone to growth streaks. In addition, it is necessary to give rotation to the growing crystal 4 in order to obtain a cylindrical crystal with a uniform composition, but this rotation stirs the center of the surface of the melt 2, resulting in a high oxygen concentration melt. A tornado-shaped turbulent flow 7 is generated from the bottom of the crucible 1 and approaches the growth surface of the growing crystal 4. As a method for reducing such heat convection 5, a method has been devised in which a crucible with a shallow bottom is used and a growing melt is automatically supplied from the outside, but this method has not yet been adopted.

(dl) Object of the Invention The object of the present invention is to provide a method for growing crystals with low oxygen concentration while blocking the influence of thermal convection and turbulence.

(el Structure of the Invention The object of the present invention is to
a second crucible with a shallow bottom and a moon-shaped side hole;
This can be achieved by bringing a seed crystal into contact with the melt in a crucible to cause crystal growth.

(f) Embodiments of the invention Invention V! In FIG. 1, 5i02 constituting crucible 1
is scraped off by thermal convection 5 and melted into the melt 2, which causes the increase in the oxygen concentration in the pulled-grown crystal 4.As a result of careful observation and observation, we found that this is due to the inner wall of the crucible. It was found that this is due to the shadowing of the turbulent flow 7 occurring in the center rather than the heat convection 5 that rises and circulates along the center. The reason σ
When the Si melt with high oxygen agglomeration, which is eluted into the melt 2 from the crucible 1 by thermal convection 5, reaches the liquid level 8, it becomes silica monoxide (
Since a considerable amount is evaporated in the form of Sin), it is expected that the oxygen concentration in the thermal convection 5 toward the center of the crucible 1 after reaching the liquid level 8 is low. On the other hand, in the turbulent flow 7 rising from the bottom to the center of the crucible 1, there is a high possibility that the Si melt having a cumulative concentration of saline acid will directly come into contact with the growing crystal 4 inside. For this reason,
In order to obtain a grown crystal 4 with a low oxygen concentration, it is sufficient to block the disturbance 7 from the bottom and use the thermal convection 5 flowing on the liquid surface 8.

Figure 2 (5) is a cross-sectional view of the crucible and growing crystal according to this example, and a plan view of JFi in the same figure. be. In other words, the inner crucible 9 provided inside is made of quartz (6) made of the same material as the crucible I.
SiO2) cross-section, diameter tri 200Cynrs]
The depth is 80 [my:] and there are multiple 11i on the sides! il
(4 in this example) through holes 10 with a diameter of 20 [mπ]
For example, using a piece of molybdenum CMO wire 11, it is suspended from the upper part and fixed in the center of the crucible 1, and the tip of the purified crystal is brought into contact with the melt 12 in the inner crucible 9 to heat the growing solid material. A carbon heater is provided to maintain the melted solution state. In this way, the turbulent flow 7 generated from the bottom of the crucible l shown in FIG.
reaches the liquid level 8 and releases high concentration oxygen in the form of SiO.The Si melt enters the inner crucible 9 through the hole 10 through f8, and the inner crucible 9 contains the melt with low oxygen content. 12 is introduced. I and the inner crucible 1
Since the bottom of the crystal 2 is shallow, the growing crystal 4 can be pulled up and grown without thermal convection.

According to this example, a grown crystal with an oxygen concentration of 1O18 [cm-3] or less and a weak contrast of growth stripes can be obtained.

(g) Effects of the Invention According to the present invention, it is possible to block the influence of thermal convection and electric current, and to increase the M length of a crystal with a low oxygen concentration.

[Brief explanation of the drawing]

In the figure, 1 is the crucible, 2 and 12 are the melt, 4 is the growing crystal, 5 is the thermal convection, 6 is the forced flow, 7 is the turbulent flow, 9 is the inner melt,
10 is a hole, Fig. 2 11-Y; ≧2--≦3ノ

Claims (1)

[Claims] A first crucible that accommodates the melt has a shallow bottom and a hole on the side. A crucible of H2 is provided, and crystal growth is performed by contacting a seed crystal with the melt in the second crucible. A crystal growth method characterized by: