JPS60155595A - Method for growing crystal - Google Patents

Abstract

PURPOSE:To avoid the vibration of a heating means and manufacture a single crystal without defects, by supplying a substantial DC current to a heating current path in growing the single crystal in a magnetic field by the Czochralski method. CONSTITUTION:A heating means 4 having an electric conduction heater arranged in the zigzag form is placed on the outer periphery of a vessel (crucible) 2 containing a semiconductor melt 3 (symbol 6 indicates a cooling jacket), and a magnetic field generating means 7 is placed on the outside thereof to pull up a single crystal 10 from the melt 3 through a single crystal 8 mounted to a pulling up chuck 9. In the above-mentioned apparatus, a curent (substantially DC) having <=4% ripple is passed through an electric conduction heater 5 of a heating means to heat the melt 3 in the vessel 2.

Description

[Detailed description of the invention] The present invention relates to a method for growing crystals.

For example, when growing a semiconductor single crystal using the Czochralski method, vibrations, thermal convection, etc. of the surface of the semiconductor melt greatly affect the quality of the grown single crystal. for example,
If the vibrations and thermal convection of the melt surface are large, the grown crystals will partially re-melt, which may cause crystal defects to occur, or may cause swirl-like defects.
Generates growth stripes.

In such Czochralski method, it has been proposed to grow the single crystal in a magnetic field, and it is known that defects such as swirls and growth stripes can be reduced by this. This is thought to be because the effective viscosity of the electrically conductive melt increases when a magnetic field is applied, suppressing thermal convection and vibrations on the melt surface. Regarding growing this single crystal in a magnetic field, for example, the Journal of Applied Physics (Journal of Applied Physics)
fApplied Physics) Vol, 37
．． No. 5. P 2021 (196B).

and Journal of Materials Science (J
Our own of Materials 5cie,
nce＞5 (1970) p8B2゜Symposium “Gallium Arsenide” Volume 5 Tomsk (Symp
osiua+ ” Ga1iu+llAr5enide
``fasc5, Tomsk) P34, etc.

However, even if such a method of growing a single crystal in a magnetic field is adopted, the occurrence of the various defects described above cannot be suppressed to a sufficient degree.

In the present invention, we have discovered that when a semiconductor single crystal is grown in a magnetic field, the heating means interacts with the magnetic field to produce unnecessary vibrations, which causes the defects described above. Based on this, improvements were made.

The present invention will be described in detail with reference to FIG. (1) in the diagram
1 generally shows a single crystal growth apparatus that can be used to carry out the method of the present invention. (2) indicates a container, such as a quartz crucible, in which a semiconductor melt, such as a silicon melt (3), is accommodated.

A heating means (4) is arranged around the outer periphery of this container (2). The heating means (4) includes energized heaters (5) arranged in a cylindrical shape along the outer peripheral surface of the container (2), for example, in a zigzag pattern. Outside this heating means (4), for example, a cylindrical heat shield or a jacket (6) that is cooled by water cooling or the like is arranged as required, and a magnetic field generating means (7), for example, is arranged outside the heating means (4). A magnet or an electromagnet that generates a DC magnetic field is arranged. (8) is a single crystal seed, and (9) is its pulling chuck.

In the present invention, in particular, heating is carried out through the heating means by passing a substantially direct current with ripple content suppressed to 4% or less.

For example, 4100G (
Gaussian) magnetic field, the heater (5) of the heating means (4)
When Ripple heated the semiconductor melt through a DC current of 3%, the outline of the melt surface of the semiconductor melt, for example, St melt (3), could be clearly observed, and there was almost no vibration on the melt surface. It was confirmed that no defects occurred, and it was also confirmed that the various defects mentioned at the beginning of the pull-grown single crystal were significantly reduced. In this case, in the absence of a magnetic field, the melt surface vibrated so violently that its outline could not be clearly observed. Incidentally, in the conventional method, the heater (5) of the heating means (4)
An alternating current is applied to the melt, and in this case, vibrations occur on the melt surface even if the above-mentioned magnetic field is applied. This is because the heater (5) through which alternating current flows vibrates in the magnetic field, and this vibration is transmitted to the container (2). Moreover, when the magnetic field is strong, the heater (5) is damaged by this vibration.

In the present invention, as described above, a nearly direct current is applied to the heater (5) of the heating means (4), and a magnetic field is applied to the single crystal growth area. There is no vibration on the melt surface, and high quality single crystals with almost no defects can be stably grown. In this case, it was confirmed that the current supplied to the heater (5) should be a direct current with a ripple of 4% or less.

Furthermore, as mentioned above, it is possible to grow stable, high-quality single crystals by applying a magnetic field because when a magnetic field is applied to a conductive liquid, its apparent viscosity is increased by the magnetohydrodynamic effect. This is thought to be due to the increase in surface tension and the decrease in convection of the melt. These suppress temperature fluctuations and vibrations on the melt surface in the single crystal growth area, and further reduce oxygen content, which will be described later.

That is, the viscosity of a conductive fluid in a magnetic field is determined by the Rayleigh-Jeffrey
s) depends on the quantity ηH.

ηH= (4/27Xd"/π2)(σμ2 H'
/, 7)...(1) (where d is the depth of the melt, σ is the electrical conductivity of the melt (Si
is about 12000Ω-10-1), μ is magnetic permeability,
(H is the strength of the magnetic field) Therefore, each time a magnetic field is applied to a semiconductor melt, for example, an SL melt, the viscosity of this melt increases, and the heating means (4) is driven by direct current to drastically reduce vibrations. In conjunction with this, the above-mentioned convection and vibrations are suppressed, the temperature is stabilized, and re-melting of the grown single crystal can also be avoided.

When a semiconductor, for example a silicon single crystal, has a high #1 element concentration, defects such as 1tm defects and oxygen precipitates may occur during heat treatment during the process of manufacturing semiconductor devices using this single crystal. , which has an adverse effect on the characteristics of the semiconductor device. However, in single-crystal semiconductors grown using the pulling method, it is desirable to lower the oxygen concentration as much as possible. However, in the normal single-crystal growth method that does not apply a magnetic field, the oxygen concentration is 1 to 1.5. X 10” at
It has a relatively high concentration of about 100 ms/cm". This is because a quartz crucible is usually used as a container for the semiconductor melt, and oxygen is supplied from this quartz (5i02) crucible and mixed into the crystal. However,
According to the present invention described above, this oxygen concentration can be reduced. This is due to the suppression of convection and vibration in the present invention, which causes the melt to flow from the quartz crucible (2) to the melt (3).
This appears to be due to a decrease in the melting and migration of oxygen components to ).

In addition, in the method of the present invention, the container (2) and the pulled single crystal (10) (therefore, the seed (8)) may be unrotated or both may be rotated relative to each other. can. Incidentally, the relationship between the number of rotations and the oxygen concentration is as shown in FIG. 2, as the number of rotations increases, the concentration increases. This seems to be due to the fact that as the crucible rotates, the amount of oxygen taken in from the quartz crucible increases as described above.

Each side of the diagram above shows the case where a single crystal is pulled and grown into a rod shape. In this case, the magnetic field generating means (7) is constituted by an electromagnet, and in the process of pulling the crystal,
By repeating the process of cutting off the electricity to the electromagnet for a certain period of time, a layer (12) with a high oxygen concentration that is likely to cause defects during subsequent heat treatment is created in a part of the pulled single crystal (10) across the axial direction of the pulled single crystal (10). can also be formed to maintain a predetermined interval. The single crystal having the defect layer (12) in this way is sliced to cut out a wafer (13) having the defect M (12) on one main surface or inside, for example. Various semiconductor elements (14) such as transistors and diodes are then formed on the other main surface. When doing this, it is possible to generate dislocations etc. in the defect layer (12) with a high oxygen concentration by going through a heat treatment process, and as is well known, the elements (14) in the wafer (13) can be generated.
) with no adverse effect on Fe.

It is possible to absorb heavy metals such as Cu and Ni, and perform Znawa gettering.

In addition, each side of the above diagram shows the case where a rod-shaped single crystal body (10) is pulled, and in this case, in order to obtain a semiconductor device, the single crystal body (10) is sliced. When a wafer is obtained, it can be grown as a plate-like single crystal during single crystal growth, and can be suitable for manufacturing solar cells, for example.

In the example shown in FIG. 3, guide plates (138 and
13b) is provided, and a plate-shaped single crystal seed (8) is used to pull and grow a plate-shaped single crystal body (10) from between the guide plates (13a) and (13b). In FIG. 3, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and redundant explanation will be omitted.

In the example shown in Fig. 4, a single crystal seed (8) is drawn laterally (almost horizontally) from the surface of the melt (3) to grow a plate-shaped single crystal (10). In this case, the same reference numerals are given to the parts corresponding to those in FIG. 1 in FIG. (15) is a heat sink.

In particular, when obtaining a plate-like single crystal in this way, vibrations, temperature, etc. on the surface of the melt (3) should be
Since this has a large effect on the properties of the single crystal, when the method of the present invention is used, stability can be maintained particularly at the melt surface, and a plate-shaped single crystal of good quality can be obtained, as described above. Furthermore, especially in the case of the example shown in FIG. 4 in which a single crystal is obtained by horizontal drawing, the melt material (not shown) is moved relative to the container (2) in order to maintain the liquid level of the melt (3) at a constant position. Application of the method of the present invention is particularly advantageous because the temperature of the replenishing melt, that is, the melting rate, can be kept constant.

As mentioned above, according to the method of the present invention, it is possible to stably grow a semiconductor single crystal, so that it is possible to efficiently obtain a single crystal with good reproducibility and uniform characteristics, and the industrial benefits are enormous. .

In the above example, the melt is a Si melt, but it may be made of other Ge, m-v group compound semiconductors, dielectrics, magnetic materials, various metals, etc., depending on the crystal to be obtained. It goes without saying that it may also be a melt or solution.

Furthermore, in addition to direct current, the current applied to the heater can almost avoid vibration due to the action of a magnetic field.
It was also confirmed that the current was alternating current or pulsating current of Hz or higher.

[Brief explanation of the drawing]

Figures 1, 3, and 4 are schematic diagrams of a single crystal growth apparatus for carrying out each side of the semiconductor single crystal growth method according to the present invention, and Figure 2 is a diagram showing the oxygen concentration and rotation. It is a curve diagram showing the relationship with speed. (11 is a single crystal growth device, (2) is a container containing the semiconductor melt (3), (4) is a heating means, (5) is its heater, (6) is a jacket, and (7) is a magnetic field generating means. , (8
) is a single crystal seed. Agent Sadato Ito Hidemori Matsukuma procedure Neichisho (method) % formula% 3,? Relationship with the case of a person who does iti correction Patent applicant address: 6-7-35J8, Kitashina-yo, Tokyo Parts-Yo-ku Name (
218) Sony Corporation Representative Director Norio Ohga - 4, Agent 6, Number of inventions increased by amendment

Claims (1)

[Claims] A container containing a semiconductor liquid, a heating means having a current path arranged around the container, a means for applying a magnetic field in a predetermined direction to the liquid, and a crystal body in contact with the liquid. means for growing crystals from the liquid material by dynamically changing the position of the current path, the current path is located at a position covered by the magnetic field, and a substantially direct current with a ripple content of 4% or less is applied to the current path. A method for growing crystals characterized by supplying.