JPH0543376A - Production of silicon single crystal - Google Patents

Abstract

(57) [Summary] When a single crystal or polycrystal silicon ingot is suspended in the air and heated and melted from the lower end of the ingot to move the heated and melted part upward, oxygen gas or oxygen plasma is applied to the heated and melted part. Method for producing single crystal silicon by spraying. It is possible to reduce the variation in the amount of oxygen precipitation in the axial direction of the ingot, and it is possible to obtain single crystal silicon in which the oxygen precipitation state is uniform, such as the amount, density and size of oxygen. Therefore, even if a single crystal silicon substrate cut out from any part of the ingot is used, variations in characteristics that occur between circuit elements such as LSI formed on the ingot are reduced, and high quality elements can be manufactured with high yield. Is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing single crystal silicon, and more particularly to a method for producing single crystal silicon used as a substrate for circuit elements such as LSI.

[0002]

2. Description of the Related Art Most of single-crystal silicon substrates currently used as substrates for circuit elements such as LSIs are a rotary pulling method from a silicon melt in a quartz crucible, that is, Czochralski method (CZ method). The single crystal silicon produced by is used. When the CZ method is used, the quartz crucible itself dissolves in the silicon melt and elutes oxygen, so that the pulled crystal has about 10 ¹⁸ atoms / cm 2.
Contains ³ oxygen impurities.

On the other hand, the solid solubility of oxygen in silicon is about 3 × 10 ¹⁷ atoms / cm ³ at a temperature of 1000 ° C., which is a typical temperature of thermal oxidation performed during LSI manufacturing. Therefore, in the heat treatment for manufacturing the LSI, oxygen contained in the silicon substrate is always in a supersaturated state, so that oxygen is likely to precipitate in the silicon substrate.

The function of oxygen in silicon single crystals is complex and diverse. When oxygen exists between crystal lattices, it has an effect of fixing dislocations and suppresses warpage of the silicon substrate due to heat treatment. On the other hand, oxygen precipitates and Si
When changed to O ₂ , silicon atoms are released due to volume expansion to form stacking faults, and when the strain is further large, minute defects such as punch-out dislocations are formed.

In a silicon substrate, if these minute defects are generated only in the interior sufficiently separated from the surface, L
In the process of manufacturing SI, the action of adsorbing contaminants such as heavy metals adhering to the surface of the silicon substrate and removing it from the active region of the element, so-called gettering action, works to obtain high quality L
It is useful for manufacturing SI. However, if the minute defects described above exist in the active region of the device, they cause an increase in leak current and are harmful to the LSI.

Therefore, as a pretreatment for LSI manufacturing, a defect-free layer (Denuded Zone, hereinafter referred to as "DZ
Layer), and a silicon substrate obtained by slicing a single crystal silicon ingot to form a defect layer (Intrinsic Gettering, hereinafter referred to as “IG layer”) inside the silicon substrate. In, for example, 110
By heating at a high temperature of about 0 ° C., oxygen near the surface is diffused outward to reduce the oxygen concentration, and then heat treatment is performed at a low temperature of, for example, about 700 ° C. to form oxygen precipitation nuclei in the silicon substrate. Processing is taking place.

[0007]

However, since the single crystal silicon produced by the CZ method is cooled under different conditions when the crystal is pulled, the ingot axial direction and the in-plane direction of the silicon substrate are not affected. Depending on the location, there are differences in the oxygen precipitation state such as the amount, size, density and structure of oxygen precipitates. Therefore, even if a heat treatment, which is a pretreatment for LSI manufacturing, is performed, the silicon substrate
Alternatively, even with a single silicon substrate, the method of forming the DZ layer and the IG layer varies depending on the location, and there is a problem in that the characteristics of the elements formed on the silicon substrate vary.

The present invention has been invented in view of the above problems, and it is an object of the present invention to provide a method for producing single crystal silicon in which the oxygen precipitation state is uniform between silicon substrates and in the plane of the silicon substrates. Has a purpose.

[0009]

In order to achieve the above object, a method for producing single crystal silicon according to the present invention is a method of suspending a single crystal or polycrystalline silicon ingot in a hollow and heating and melting from the lower end of the ingot. When moving the heating / melting section upwards, oxygen gas or oxygen plasma is blown to the heating / melting section.

[0010]

According to the above-mentioned method, when a single crystal or polycrystalline silicon ingot is suspended in the air and heated and melted from the lower end of the ingot to move the heated and melted part upward, oxygen is added to the heated and melted part. Since the gas or oxygen plasma is blown, the variation in the amount of precipitated oxygen in the axial direction of the ingot is reduced, and a single crystal silicon ingot in which the precipitated state of oxygen such as the amount, density and size of oxygen is uniform can be obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for producing single crystal silicon according to the present invention will be described below with reference to the drawings. Reference numeral 11 in FIGS. 1 and 2 schematically shows a high-purity polycrystalline silicon ingot as a material. This polycrystalline silicon ingot 1
A high-frequency coil 12 for heating the polycrystalline silicon ingot 11 is installed around the periphery of 1. As a method for heating the polycrystalline silicon ingot 11, in addition to the high frequency coil 12 described above, there is a method using an infrared lamp, a carbon heater, a method using a laser beam, an electron beam, or the like.

The method for producing single crystal silicon will be described below. First, the high-purity polycrystalline silicon ingot 11 is attached to the crystal support jig 13. Next, the periphery of the polycrystalline silicon ingot 11 is evacuated, and then argon gas is introduced to make it 5 Torr. After that, by supplying high-frequency power to a high-frequency coil 12 from a high-frequency oscillator (not shown), the lower end of the polycrystalline silicon ingot 11 is heated to form a melt zone and weld to the seed crystal 14. After that, so-called squeezing (diameter of about 3 mm, length of about 30 mm) is carried out to extract dislocations on the surface, and it is confirmed by crystal habit lines that dislocations have not occurred.

As shown in FIG. 1, 99.9999% at 10 liters / minute from the nozzle 15 for jetting gas.
The oxygen gas of the molten portion 1 of the polycrystalline silicon ingot 11
Spray 1b and maintain the gas pressure at about 15 Torr.
Then, the polycrystalline silicon ingot 11 is recrystallized while adjusting the downward moving speed and high frequency power to form a single crystal silicon ingot 11a having a diameter of 5 inches and an ingot length of 1100 mm. As a gas jet nozzle for blowing oxygen gas, a nozzle body 16 formed by an annular pipe as shown in FIGS. 2 and 3.
Oxygen gas is blown to the melted portion 11b more uniformly by using the one having a plurality of holes 16a formed inside thereof. Alternatively, 99.9999% oxygen gas may be previously introduced into the furnace so that the gas pressure is about 15 Torr, and oxygen plasma may be generated in the vicinity of the melting portion.

In order to measure the distribution of interstitial oxygen concentration in the axial direction of the single crystal silicon ingot 11a thus obtained, the single crystal silicon ingot 11a is sliced to a desired thickness to form a single crystal silicon substrate. It was made. The distribution of interstitial oxygen concentration in the axial direction of the ingot in this single crystal silicon substrate is shown by ◯ in FIG. Further, FIG. 4 shows that the above-mentioned single crystal silicon substrate was further heated at 800 ° C. for 5 hours at 1000 ° C. in an oxygen gas atmosphere.
The heat treatment was carried out for 15 hours in the above, and the distribution of the interstitial oxygen concentration after this heat treatment in the ingot axis direction is also shown by ●. The interstitial oxygen concentration was measured using a Fourier transform infrared spectrometer (FT-IR).

As is clear from FIG. 4, the variation in the amount of oxygen precipitation (interstitial oxygen concentration of the single crystal silicon ingot-interstitial oxygen concentration of the single crystal silicon substrate after heat treatment) in the axial direction of the ingot is within ± 25%. Has become
It was found that single crystal silicon having a uniform oxygen precipitation state such as the amount, density and size of oxygen was obtained.

As a comparative example, a single crystal silicon substrate was prepared using a single crystal silicon ingot grown by the CZ method, and the distribution of interstitial oxygen concentration in the single crystal silicon substrate in the axial direction of the ingot is shown in FIG. Indicated. In FIG. 5, ◯ indicates the distribution of the interstitial oxygen concentration of the single crystal silicon ingot by the CZ method, and ● indicates the ingot of the single crystal silicon substrate after the heat treatment under the same conditions as in the above-mentioned embodiment. 2 shows the distribution of interstitial oxygen concentration in the axial direction of.

As is apparent from FIG. 5, the variation in the amount of oxygen precipitation between the single crystal silicon substrate produced by using the single crystal silicon ingot grown by the CZ method and the single crystal silicon substrate after the heat treatment is as follows. It was as large as ± 55% in the axial direction of the ingot.

As described above, by heating and melting the single crystal silicon ingot while adding oxygen atoms, and then recrystallizing the same, it is possible to reduce the variation in the amount of oxygen precipitation in the axial direction of the ingot, and to reduce the oxygen content. The single crystal silicon ingot 11a in which the oxygen precipitation state is uniform, such as the amount, density and size, can be obtained. Therefore, no matter which part of the single crystal silicon ingot 11a is used, the variation in characteristics generated between circuit elements such as LSI formed on the single crystal silicon substrate is reduced, and high-quality elements can be produced with good yield. It becomes possible to produce.

[0019]

As described above in detail, in the method for producing single crystal silicon according to the present invention, the single crystal or polycrystalline silicon ingot is suspended in the hollow, and the single crystal or polycrystalline silicon ingot is heated and melted from the lower end portion of the ingot. When moving the heating / melting section upward, since oxygen gas or oxygen plasma is blown to the heating / melting section, it is possible to reduce the variation in the amount of oxygen precipitation in the axial direction of the ingot, the amount, density and size of oxygen, etc. As a result, single crystal silicon in which the oxygen precipitation state is uniform can be obtained. Therefore, even if a single crystal silicon substrate cut out from any part of the single crystal silicon is used,
Variations in characteristics that occur between circuit elements such as LSIs formed on this are reduced, and high-quality elements can be manufactured with high yield.

[Brief description of drawings]

FIG. 1 is a schematic partial cross-sectional view showing a manufacturing process of a single crystal silicon substrate according to the present invention.

FIG. 2 is a schematic partial cross-sectional view showing a manufacturing process of a single crystal silicon substrate according to the present invention.

FIG. 3 is a plan view showing another embodiment of the nozzle.

FIG. 4 is a graph showing the distribution of interstitial oxygen concentration in the axial direction of a single crystal silicon ingot and a single crystal silicon substrate after heat treatment.

FIG. 5 is a graph showing the distribution of interstitial oxygen concentration in the axial direction of the single crystal silicon ingot according to the comparative example and the single crystal silicon substrate after the heat treatment.

[Explanation of symbols]

 11 Other crystal silicon ingot 11a Single crystal silicon ingot 11b Melting part

Claims (1)

[Claims] 1. A single crystal or polycrystal silicon ingot is suspended in the air, and when the lower end of the ingot is heated and melted to move the heated and melted part upward, oxygen gas or oxygen plasma is applied to the heated and melted part. A method for producing single crystal silicon, which comprises spraying.