JPS58151393A - Production of silicon crystal - Google Patents

Abstract

PURPOSE:To obtain an Si crystal having uniform density of internal defects, by subjecting the Si crystal to high frequency induction heating while moving a high-frequency coil provided concentrically around the Si crystal in the axial direction of pulling the crystal at the speed corresponding to the oxygen concn. in the axial direction of the Si crystal. CONSTITUTION:An Si crystal 1 is rotated as shown by an arrow 3 and while a coil 2 is moved from the top part of the Si crystal ingot 1 toward the bottom part as shown by an arrow 4, high-frequency electric power is supplied from the coil 3 and the Si crystal ingot is heated by an induction heating method, whereby the ingot is subjected to a low-temp. heating treatment. The moving speed of the coil 2 is so controlled as to be proportional to the oxygen concn. in the ingot 1 in each position. The ingot is thereafter subjected to two stages of ordinary heating treatments, whereby the ingot is formed to have the density of internal defects approximately uniform over the entire length thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION (♂) Technical Field of the Invention The present invention relates to a method of manufacturing a silicon crystal, and more particularly to a method of uniformly forming crystal defect nuclei within a silicon crystal.

(bl Technology background) In the production of ultra-LSIs, which have become increasingly highly integrated in recent years, by subjecting semiconductor crystals to a certain type of heat treatment, trace amounts of heavy metals contained within the semiconductor crystals are precipitated into internal defects in the crystals. There is a tendency for the so-called intrinsic gettering (hereinafter abbreviated as IG) effect to be actively utilized.

IcI Prior Art and Problems The internal defects in the semi-integral crystal described above cause the semiconductor crystal to
By heat treatment at 0 to 900 (°C) (hereinafter referred to as low temperature treatment), interstitial oxygen contained within the crystal precipitates to form defect nuclei, and further heat treatment at approximately 1100 (t) ( 211 (hereinafter referred to as high temperature treatment)
Due to the heat treatment, the defect nuclei grow and are formed.

Active use of the above-mentioned IG effect means that internal defects are formed in the crystal in this way, and heavy metals contained within the crystal are precipitated into the internal defects in the heat treatment process during or in the subsequent heat treatment process. , which aims to obtain crystal characteristics suitable for manufacturing semiconductor devices.

The density of the crystal defect nuclei mentioned above is the oxygen (0
1: The subscript i means interstitial (interstitial) depending on the concentration and the low temperature treatment time. That is, the density of internal defect nuclei increases as the oxygen concentration increases and as the low temperature treatment time increases.

On the other hand, oxygen (Oj) contained in the silicon (St) crystal
) H, check the silicon (Si) crystal (CZ
) method, it mixes into the molten silicon (Si) inside the quartz crucible, and its concentration distribution is not uniform, as shown in Figures 1 and 2 (described later).
Seed side of silicon (Si) crystal ingot l (Top
) is ^(, the other end (B.

It becomes lower as it goes toward the Ltom) side. Therefore, the IG effect is not uniform, and the T of the crystal ingot.

It is strong on the p side and becomes weaker on the Bo and ttom sides.

Since commonly used silicon (St) crystals have such an oxygen ((1:) concentration distribution), the internal defect density is not uniform, and therefore the IG effect cannot be made uniform.

(dl) OBJECTS OF THE INVENTION An object of the present invention is to provide a method for manufacturing a silicon (Si) crystal that can eliminate the above-mentioned problems and make the internal defect density uniform.

(8) Structure of the Invention The feature of the method for manufacturing a silicon crystal of the present invention is that a high frequency coil is provided concentrically around the silicon crystal, and the high frequency coil or the silicon crystal is moved in the direction of the pulling axis of the silicon crystal. The present invention includes the step of subjecting the silicon crystal to a heat treatment using a high frequency induction heating method while moving the silicon crystal at a speed corresponding to the oxygen concentration in the axial direction.

(fl Embodiments of the Invention Below, an embodiment of the method for manufacturing silicon crystal of the present invention will be described in the first embodiment.
Explain using Figures 4 to 4.

In Fig. 1, l is silicon (St
) Crystal ingot, 2 is a high frequency coil arranged concentrically with the St crystal l.

In this embodiment, as shown in the figure, the Si crystal 1 is rotated as shown by the arrow 3, and the coil 2 is rotated from the Top part of the St crystal ingot 1 as shown by the arrow 4.
While moving toward the m section, the Si crystalline influenium is heated by an induction heating method in which high-frequency power is supplied from the coil 3, and the above-mentioned low-temperature heat treatment is performed. The temperature is therefore selected in the range of approximately 600-900°C ('t:). In this example, since the frequency was approximately 300 (kHz), approximately 10 (kW) of power was supplied from a frequency power supply.

As shown in FIG. 2, the Si crystal ingot 1 is
Since A has a one-time distribution, the moving speed of the coil 2 is
As shown in FIG. 3, the oxygen concentration is controlled to be proportional to the oxygen concentration inside the crystal ingot l at each position. In this way, the sweep speed of the coil 2 is made faster in areas where the oxygen concentration is high and slowed in areas where the oxygen concentration is low. That is, the heat treatment time for each part of the Si crystal ingot 1 is shorter on the T o p side of the SS crystal ingot 1, and shorter on the B side of the SS crystal ingot 1.
Make it longer towards the ottom side.

Thereafter, by carrying out the usual two-step heat treatment described above, it was possible to form a substantially uniform internal defect density over the entire length of the ingot.

Figure 4 shows the internal defect density (curve A) of the Si crystal ingot obtained in this example, and the internal defect density (curve B) of the Si crystal ingot that was subjected to only the conventional two-step heat treatment.
). In both of the above two-step heat treatments, the first step was performed at a temperature of approximately 650 (°C) for approximately 3 hours, and the second step was performed at a temperature of approximately 1100 (°C) for approximately 5 hours.
It was set as [time].

The vertical axis of the figure shows the amount of decrease in oxygen concentration, but since internal defects are formed by precipitation of interstitial oxygen contained in the ingot as described above, the amount of decrease in oxygen concentration is It can be imaged as defect density.

Si manufactured by the conventional manufacturing method shown in curve B in the same figure
While the internal defect density of the crystal ingot varies significantly depending on the location, the S
In the i-crystal ingot, the internal defect density has small variations in any part and is substantially uniform. Therefore, according to this embodiment, the IG effect is uniform over the entire length of the obtained open-hole ingot, making it possible to effectively use the crystal ingot.

The subsequent cutting and polishing of the crystal ingot for producing the Si substrate, the element forming process for forming desired elements on the Si substrate, etc. may all be carried out according to normal manufacturing methods.

In addition, although the coil 2 was moved in the above example,
Of course, the silicon crystal ingot 1 may be moved.

DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention provides a method for manufacturing a silicon crystal that can form a uniform internal defect density.

[Brief explanation of the drawing]

FIG. 1 is a side view of essential parts showing an embodiment of the present invention, FIG. 2 is a curve diagram showing the interstitial oxygen concentration distribution inside the silicon crystal ingot, and FIG. 3 is a curve diagram showing the sweep speed of the coil. FIG. 4 is a curve diagram showing the internal defect density of the St crystal ingot obtained by this example in comparison with that of the conventional manufacturing method. In the figure, 1 is a silicon (Si) crystal ingot, 2
is a coil, 4 is an arrow line indicating the sweeping direction of the coil 2, and A is a curve indicating the internal defect density as an effect of the present invention.

Claims (1)

[Claims] A high frequency coil is disposed concentrically around the silicon crystal, and while the high frequency coil or the silicon crystal is moved in the axial direction at a speed corresponding to the oxygen concentration in the pulling axis direction of the silicon crystal, the high frequency induction heating method is applied to the silicon crystal. 1. A method for producing a silicon crystal, comprising the step of subjecting a silicon crystal to heat treatment to generate crystal defect nuclei inside the silicon crystal.