JPH021119B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) 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 defects inside a silicon crystal.

(b) Background of the technology In manufacturing VLSIs, 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 and other substances contained within the semiconductor crystals are precipitated into internal defects in the crystals. The so-called intrinsic gettering (hereinafter abbreviated as IG) effect is
There is a tendency for it to be actively used.

(c) Prior art and problems The internal defects in the semiconductor crystal described above can be removed by heating the semiconductor crystal at 600 to 900 [°C] (hereinafter referred to as low temperature treatment). Oxygen precipitates to form defect nuclei, and then the defect nuclei grow and are formed by a two-step heat treatment at about 1100 [° C.] (hereinafter referred to as high temperature treatment).

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 during the heat treatment process or the subsequent heat treatment process. , which aims to obtain crystal characteristics suitable for manufacturing semiconductor devices.

The density of the crystal defect nuclei depends on the concentration of oxygen (O _i : subscript i means interstitial) contained inside the crystal 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, the oxygen (O _i ) contained in the silicon (Si) crystal mentioned above is mixed into the molten silicon (Si) inside the quartz crucible when the silicon (Si) crystal is pulled by the Czochralski (CZ) method. ,
The concentration distribution is not uniform; as shown in Figures 1 and 2 (described later), the concentration is high on the seed side (Top) of the silicon (Si) crystal ingot 1 and decreases as it goes to the other end (Bottom) side. Become. Therefore, the IG effect is not uniform, and the
Stronger on the Top side, weaker on the Bottom side.

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

(d) Object of the Invention An object of the present invention is to solve the above-mentioned problems and provide a method for manufacturing a silicon (Si) crystal that can uniformize the internal defect density.

(e) Structure of the Invention The method for producing a silicon crystal according to the present invention is characterized in that a high-frequency coil is provided concentrically around the silicon crystal, the high-frequency coil or the silicon crystal is moved in the direction of the pulling axis of the silicon crystal, and Heat treatment is applied to the silicon crystal by a high frequency induction heating method while changing its moving speed in accordance with the oxygen concentration at the high frequency coil position of the silicon crystal, followed by heat treatment at a first temperature and The method includes the step of sequentially performing heat treatment at a higher second temperature to generate crystal defects at a uniform density inside the silicon crystal.

(f) Embodiments of the Invention An embodiment of the silicon crystal manufacturing method of the present invention will be described below with reference to FIGS. 1 to 4.

In FIG. 1, 1 is a silicon (Si) crystal ingot prepared by the CZ method, and 2 is a high frequency coil arranged concentrically with the Si crystal 1.

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 Si crystal ingot 1 as shown by the arrow 4.
Coil 3 while moving it toward the bottom part.
The Si crystal ingot 1 is heated by an induction heating method that supplies higher frequency power, and subjected to the above-mentioned low-temperature heat treatment. Therefore, the temperature is selected within the range of approximately 600 to 900 [°C]. In this example, the frequency is approximately 300 [k
The experiment was carried out by supplying approximately 10 [kW] of power from a high-frequency power supply of [Hz].

Since the Si crystal ingot 1 has an oxygen concentration distribution as shown in FIG. 2, the moving speed of the coil 2 is controlled to be proportional to the oxygen concentration inside the crystal ingot 1 at each position as shown in FIG. . 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, Si
The heat treatment time for each part of the crystal ingot 1 is shortened on the top side of the Si crystal ingot 1 and lengthened as it goes to the bottom 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 ingot length.

Figure 4 compares the internal defect density (curve A) of the Si crystal ingot obtained in this example with the internal defect density (curve B) of the Si crystal ingot that was subjected to only the conventional two-step heat treatment. show. Note that the above 2
In both stage heat treatments, the first step is approximately
The second step was carried out for about 3 hours at a temperature of 650°C, and for about 5 hours at a temperature of about 1100°C.

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 regarded as defect density.

The internal defect density of the Si crystal ingot manufactured by the conventional manufacturing method shown by curve B in the same figure varies significantly depending on the location, whereas the internal defect density of the Si crystal ingot manufactured by this example shown by curve A differs depending on the location. However, the variation in the internal defect density is small and approximately uniform. Therefore, according to this embodiment, the IG effect is uniform over the entire length of the obtained crystal ingot, so that the crystal ingot can be used effectively.

The subsequent steps of cutting and polishing the crystal ingot for creating the Si substrate, or the element forming step for forming desired elements on the Si substrate, etc., may all be carried out in accordance with conventional manufacturing methods.

Although the coil 2 was moved in the above embodiment, it goes without saying that the silicon crystal ingot 1 may also be moved.

(g) Effects of the Invention As explained above, the present invention provides a method for manufacturing a silicon crystal that can form a uniform internal defect density.

[Brief explanation of drawings]

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

Claims (1)

[Claims] 1. A high frequency coil is provided concentrically around the silicon crystal, the high frequency coil or the silicon crystal is moved in the direction of the pulling axis of the silicon crystal, and the moving speed is adjusted to the oxygen concentration at the position of the high frequency coil of the silicon crystal. The silicon crystal is heated by a high-frequency induction heating method while the silicon crystal is heated in a corresponding manner, and then a heat treatment at a first temperature and a heat treatment at a second temperature higher than the first temperature are sequentially performed to heat the silicon crystal. A method for producing a silicon crystal, comprising a step of generating crystal defects at a uniform density inside the crystal.