JPH05238873A - Production of silicon single crystal - Google Patents

Abstract

PURPOSE:To obtain, through Czochralski process, silicon single crystal developing few oxidation-induced laminate defects by using a quartz crucible with electric charge neutralized by destaticization. CONSTITUTION:A quartz crucible to be used is destaticized in advance to neutralize the electric charge thereon. The destaticization is pref. such a process that electrons are emitted taking advantage of photoelectric effect and the electrons thus emitted are bound to gaseous atoms or molecules to form negative ions. And, in a practical production site for silicon single crystal, it is preferable n terms of operating efficiency that an ionizer be installed and operated in a clean room and a quartz crucible is left to stand for a specified time to carry out destaticization. Thence, the crucible destaticized is set in a pull device and the objective silicon single crystal is produced through Czochralski process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for producing a silicon single crystal by the Czochralski method using a quartz crucible. More specifically, the oxidation-induced stacking fault (O
The present invention relates to a method for producing a silicon single crystal by pulling a silicon single crystal with less generation of SF) by the Czochralski method.

[0002]

2. Description of the Related Art A silicon single crystal is manufactured mainly by the Czochralski method. The Czochralski method involves charging high-purity polycrystalline silicon, which is a raw material for pulling, into a crucible, melting it in an inert gas atmosphere,
This is a method in which a silicon single crystal as a seed crystal is immersed in this silicon melt and pulled up. The crucible used in the Czochralski method is required to have heat resistance at a high temperature of 1414 ° C., which is the melting point of silicon, and a quartz crucible made of quartz glass is usually used.

On the other hand, higher integration of devices using a silicon wafer manufactured from a silicon single crystal is continuously progressing, and accordingly, quality requirements for the silicon wafer are naturally becoming stricter. The quality of this silicon wafer depends largely on the original crystal quality of the silicon single crystal, and one of them, the oxidation-induced stacking fault (OSF) of the silicon single crystal, adversely affects the quality of the silicon wafer.

[0004]

However, since the silicon single crystal manufactured by the Czochralski method using the quartz crucible as described above has a high oxidation-induced stacking fault density, the crystal quality of the silicon single crystal is different from that of the device. However, there is a problem in that the quality requirements based on the high integration degree of are not always sufficiently satisfied.

In view of the above problems, the present inventors have diligently studied a method for producing a silicon single crystal by the Czochralski method in order to reduce the occurrence of oxidation-induced stacking fault (OSF) of the silicon single crystal. As a result, surprisingly, the oxidation-induced stacking fault (OSF) of a silicon single crystal ingot was observed when a quartz crucible that had been subjected to some static elimination treatment was used.
The unexpected fact that the density is decreased was found, and the present invention was completed.

An object of the present invention is to provide an oxidation-induced stacking fault (OS).
F) The purpose of the present invention is to provide a silicon single crystal having a low density and improve the deterioration of crystal quality due to the oxidation-induced stacking fault (OSF) of the silicon single crystal.

[0007]

That is, the present invention is directed to a quartz crucible that has been subjected to static elimination treatment including a step of neutralizing the charge of the quartz crucible in the production of a silicon single crystal by the Czochralski method using a quartz crucible. Is used to pull up a Czochralski method silicon single crystal.

The present invention will be described below. In the present invention, the static elimination treatment including the step of neutralizing the electric charge of the quartz crucible can be performed by any method within a range not impairing the effect of the present invention, but in principle, a method utilizing a photoelectric effect is used. Is preferred.

That is, when light is incident on a substance, a nuclear electron in the substance absorbs the energy of incident light and leaves its orbit to become a free electron. This is a step of neutralizing the electric charge of the quartz crucible and performing a neutralization process by a phenomenon in which the emitted photoelectrons are combined with a gaseous atom or molecule to generate a negative ion by utilizing an external photoelectric effect for releasing the electric charge.

Here, the energy of electrons emitted by the photoelectric effect is E = hv-w (h: Planck's constant,
v: frequency of light, w: minimum energy required to emit electrons). Therefore, in order to perform the static elimination processing used in the present invention, it is necessary to irradiate the irradiation target object with light having a frequency equal to or higher than the limit frequency v ₀ given by w / h = v _0. The minimum energy required to emit a given electron is represented by the sum of the ionization energy of the irradiated solid and the work (work function) required for the electron to fly out from the surface boundary.

For example, in the air atmosphere, a metal is selected as the object to be irradiated, the wavelength of the irradiation light is selected to be higher than the ionization energy (work function) of the metal, the light is irradiated, and the emitted photoelectrons are emitted. The static elimination can be performed by leaving the quartz crucible in an atmosphere in which negative ions in which gaseous atoms or molecules are bonded are generated.

Usually, an ultraviolet light irradiation lamp such as a mercury lamp or a xenon lamp, which has a large light energy, is used to emit electrons by irradiating light to a metal irradiation object having an ionization energy smaller than the light energy of the irradiation lamp. The emitted electrons combine with the gaseous atom or molecule to generate negative ions, but at the same time, positive ions also generate about half of the negative ions depending on the conditions, so the negative ions repel the quartz crucible. However, only the positive ions are involved in the neutralization of the electric charge of the quartz crucible, and the quartz crucible is discharged. Therefore, the metal impurities charged and attached to the surface of the quartz crucible are released from the charge, and as a result, the metal impurities can be removed.

The number of emitted electrons is proportional to the intensity of irradiation light, and the limit frequency of irradiation light required to emit electrons is
Although it depends on the non-irradiated object, in the present invention, it suffices that the quartz crucible be destaticized, and the irradiation lamp, the irradiated object, and other conditions for performing the photoelectric effect are appropriately selected within a range that does not impair the effects of the present invention. It goes without saying that you can do it.

It is important that the static elimination treatment of the present invention is carried out without the quartz crucible being contaminated with impurities or the like. Therefore, it is preferable to carry out in an ultrahigh-purity gas atmosphere in which impurities in the atmosphere do not adhere to the quartz crucible and become a pollution source, and when carried out in air, it is preferable to carry out in a clean room.

In the static elimination treatment of the present invention, for example, a method of generating static ions by spark discharge or corona discharge to eliminate static electricity is considered to be unfavorable. This is because there is a high possibility that fine particles will be generated at the tip of the discharge electrode due to the sputtering effect of the ions, and that dust, which may be a contamination source of the quartz crucible, will occur. In the present invention, the static elimination treatment utilizing the principle of photoelectric effect is preferable because there is no spattering action which causes dust generation.

A method of removing the static electricity by handling the quartz crucible with a grounded conductive material is also conceivable. However, the quartz crucible is likely to be contaminated during handling, and from the viewpoint of workability. Is not the preferred method.

At an actual silicon single crystal manufacturing site, an ionizer is installed and operated in a clean room and the quartz crucible is left for a predetermined time to carry out the static elimination treatment of the present invention. The quartz crucible is used to perform the Czochralski method. From the viewpoint of work efficiency, it is preferable to carry out the silicon single crystal pulling production by

The quartz crucible, which has been subjected to the static elimination treatment as described above, is installed in a pulling machine (chamber) and a silicon single crystal is manufactured by the Czochralski method.

[0019]

In the present invention, the effect is obtained when the quartz crucible is neutralized before the quartz crucible is installed in the furnace of the pulling machine (chamber) and the single crystal is pulled by the Czochralski method. is there. When the quartz crucible is installed in the furnace of a pulling machine and heated to a high temperature, high temperature conductivity occurs. That is, in the pulling of a silicon single crystal, an electric circuit is usually formed between the molten silicon and the carbonaceous furnace material via the quartz crucible while the silicon raw material is melted in the quartz crucible. It is considered that the quartz crucible is discharged. However, at this point, even if the metal impurities charged and adhered to the surface of the quartz crucible are more easily removed than the static elimination of the quartz crucible, there is naturally no means for removing them, so that the effect of the present invention can be obtained. I can't.

In the manufacturing process in which a silicon single crystal is pulled by the Czochralski method, the present inventors, as described above, perform a predetermined static elimination treatment on the quartz crucible before pulling the silicon single crystal. The inventors have found the effect of reducing the generation of oxidation-induced stacking faults (OSF) in a pulled up silicon single crystal, and have solved the technical problems of the prior art.

[0021]

EXAMPLES Specific examples of the present invention will be described in detail below. However, the present invention is not limited to the scope of the examples shown below.

The present invention is carried out using a static eliminator utilizing the photoelectric effect. A xenon lamp is attached as irradiation light to an aluminum chamber that can store a quartz crucible, and nitrogen gas is circulated. The xenon lamp is set at a position where it can directly irradiate the inner wall of the aluminum chamber, and the quartz crucible for static elimination is set in the chamber at a position where the xenon irradiation light is not blocked.

When the inner wall of the aluminum chamber is irradiated with xenon lamp light having a wavelength of 200 nm, electrons are emitted from the inner wall of the aluminum by the photoelectric effect and negative ions are generated. In this case, the maximum energy of xenon light and the ionization energy of aluminum of the non-irradiated object are 6.2 eV and 6.0 eV, respectively. Although the generated ions can be analyzed by attaching an ion counter to the chamber, the amount of generated ions by this device is tens of millions of negative ions and about half of the positive ions. The amount of negative ions generated can be adjusted by the amount of light, but as the concentration of negative ions in the atmosphere around the quartz crucible is higher, the amount of positive ions generated is proportional to the concentration of negative ions, so the initial potential of the quartz crucible decreases. The static elimination can be performed quickly and in a short time. The static elimination treatment is performed using a quartz crucible that is washed with pure water and dried in a usual manner. The quartz crucible thus destaticized is usually stored in a clean room until the silicon single crystal is pulled.

A silicon single crystal manufactured by the Czochralski method using a quartz crucible that has been subjected to static elimination processing using this apparatus, and a silicon pulled up using a quartz crucible that has not been subjected to static elimination processing by this apparatus. A significant difference is observed in the density of oxidation-induced stacking faults (OSF) generated between the single crystal and the single crystal.

In the present embodiment, a xenon lamp was used as the light source and aluminum was used as the object to be irradiated, but it is of course possible to carry out static elimination processing by a device other than this light source and object to be irradiated. For example, a mercury lamp can be used instead of the xenon lamp, and the material forming the chamber may be a material having a small ionization energy, that is, a work function, and an alloy may be used instead of a pure metal. It is possible.

Next, a description will be given of an embodiment in which an ionizer is installed and operated in a clean room to remove electricity from a quartz crucible. The quartz crucible, which was washed with pure water by spraying pure water from a spray nozzle according to a conventional method, was dried in a dryer at 70 ° C. in a nitrogen atmosphere for 1 hour, and then an ionizer with an output of 20 kV or less was installed in a downflow type clean room (c
(less than 1000) and allowed to cool for 1 hour and 30 minutes for static elimination.

The ionizer was installed on the ceiling of the clean room through a filter. The quartz crucible washed with water was allowed to stand still on the floor of the perforated plate of the floor of the downflow type clean room, and the ionizer was operated at an output of 4 kV. 1
After the half hour, the quartz crucible was cooled to room temperature, and then the quartz crucible was stored in a predetermined place in a clean room. The quartz crucible was installed in a pulling machine and the ionizer in the clean room was operated until the silicon single crystal was manufactured. The charge amount of the quartz crucible after cooling was -2k.
It was on the order of V.

Then, the quartz crucible having been subjected to the static elimination treatment was installed on the graphite susceptor in the furnace of the pulling machine, and the 6-inch φN type <100 was prepared by the Czochralski method according to the usual method.
> The silicon single crystal was pulled up to manufacture a silicon single crystal rod.

In a comparative example, a quartz crucible stored in a clean room in which the static eliminator was not operated and stored by cooling in the same manner as in the example was used under the same conditions as in the example.
An inch φ N type <100> silicon single crystal was manufactured.

Oxidation-induced stacking faults (OS) of the silicon single crystals (50 pull-ups) manufactured in the above Examples and Comparative Examples.
F) Density, that is, the number of oxidation-induced stacking faults (OSF) per square centimeter was measured.

The measurement results are shown in FIG. In FIG. 1, the vertical axis represents the oxidation-induced stacking fault (OSF) density (pieces / cm ² ), and the horizontal axis represents the number of silicon single crystals produced by the methods of Examples and Comparative Examples. As is clear from FIG. 1, the silicon single crystal manufactured by the method of the present invention has a reduced oxidation-induced stacking fault (OSF) density as compared with the comparative example of the conventional method.

[0032]

According to the manufacturing method of the present invention, it is possible to manufacture a silicon single crystal in which generation of oxidation-induced stacking fault (OSF) is small. The silicon single crystal manufactured according to the present invention provides a silicon wafer with low oxidation-induced stacking fault (OSF).

[Brief description of drawings]

FIG. 1 is an oxidation-induced stacking fault (OSF) of a silicon single crystal.
It is a graph showing the relationship between density and the number of pull-ups.

Claims (3)

[Claims] 1. A method for producing a silicon single crystal by the Czochralski method using a quartz crucible, characterized by using a quartz crucible that has been subjected to static elimination treatment for neutralizing the charge of the quartz crucible. Method. 2. A phenomenon in which, in the static elimination treatment for neutralizing the electric charge of the quartz crucible, an electron is emitted by utilizing a photoelectric effect, and the emitted electron is bonded to a gaseous atom or molecule to generate a negative ion. The method for producing a silicon single crystal according to claim 1, which is carried out by. 3. The method for producing a silicon single crystal according to claim 1, wherein the static elimination treatment for neutralizing the electric charge of the quartz crucible is performed by an ionizer in a clean room.