JPH0687687A - Device for pulling up silicon single crystal - Google Patents

Abstract

PURPOSE:To prevent the deterioration of parts by forming an air passage provided inside a heat insulating shield or between an exterior material and the shield and communicating the lower end of the air passage of the heat insulating shield with the opening provided close to the opening of a crucible with an inert gas outlet. CONSTITUTION:A seed crystal is dipped in the molten Si 2 in a quartz crucible 1, the crucible 1 and seed crystal are rotated, and the crystal is grown. The wall surface of the crucible 1 is rubbed with the molten Si 2 by the heat convection resulting from the nonuniformity of density due to the temp. difference in the molten Si 2 in the crucible 1 and by the convection resulting from the rotation of the crucible 1 and Si single crystal 5, O2 is dissolved from the crucible 1, and the dissolved O2 forms SiO which is vaporized. Meanwhile, a pulling-up chamber 6 is evacuated, an inert gas 7 such as Ar is introduced from the upper part and discharged together with the SiO from an inert gas outlet 16 through the opening 18 at the upper end of a double-walled heat insulating shield 4 and an air passage 17. Consequently, the deterioration of the single crystal due to the deposition of an SiO forming material such as a graphite member is prevented, and the quality of the Si single crystal to be pulled up is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon single crystal pulling apparatus, and more specifically, to eliminate the deposition of unnecessary substances on a member which is susceptible to contamination in the pulling apparatus even during a pulling operation for a long period of time. The present invention relates to a silicon single crystal pulling device that can extend the usable period of time and simplify cleaning and dismantling work.

[0002]

2. Description of the Related Art It is well known that semiconductor devices are made from a substrate obtained from a high-purity silicon single crystal ingot. The high-purity single crystal ingot is sliced with a diamond blade, further subjected to lapping, etching with a chemical agent, and then subjected to mirror finishing, and then used as a starting material substrate for semiconductor integrated circuits, for example.

In recent years, with the progress of semiconductor technology, the need for more precise control of the dopant concentration, the concentration of impurities other than the dopant, the lattice defect density, etc. has increased, and the semiconductor single crystal pulling apparatus has the above precision. It is required to perform such precise control over a long period of time, and to perform cleaning and dismantling work as little as possible.

Conventionally, the Czochralski method has been adopted for pulling a silicon single crystal, and an example thereof is shown in FIG. In FIG. 2, 1 is a crucible for containing the silicon melt 2, 3 is a heater provided on the outer periphery of the crucible 1, 4 is a heat shield provided on the outer periphery of the heater 3,
5 is a silicon single crystal that is being pulled up.

When a silicon single crystal is manufactured by the Czochralski method, a quartz crucible is used as the crucible 1. Therefore, oxygen is dissolved in the silicon melt from the quartz crucible, which is converted into the silicon single crystal. It is known to be captured. This is because the silicon melt acts on the quartz crucible by the thermal convection of the silicon melt contained in the quartz crucible and the forced convection generated by the rotation of the crucible during pulling, whereby SiO ₂ and Si forming the quartz crucible are formed. A reaction occurs, SiO is generated by this reaction, this SiO is once taken into the melt, most of the SiO is evaporated from the surface of the melt, and the residue is taken into the silicon single crystal. is there.

Since this SiO raises the interstitial oxygen concentration in the silicon single crystal to be produced, it causes defects in some cases, and causes the getter effect in other cases, so the oxygen concentration taken into the crystal is increased. Needs to be controlled with high precision.

Therefore, if the pulling chamber 6 is a completely closed system, the SiO evaporated from the silicon melt is remelted in the silicon melt, and the SiO concentration in the pulling chamber 6 changes every moment, so that it is constant. It becomes difficult to pull up a single crystal having an oxygen concentration. Therefore, the inert gas 7 is introduced into the pulling chamber 6, and SiO in the pulling chamber 6 is caused to flow together with the inert gas 7 so that the SiO concentration in the pulling chamber 6 is brought to a steady state.

[0008]

However, in the conventional silicon single crystal pulling apparatus shown in FIG. 2, after the inert gas 7 is made to flow from above the pulling chamber 6 and the surface of the silicon melt 2 is melted, It passes through a gap 9a formed between the crucible 1 and the heater 3 and a gap 9b formed between the heater 3 and the heat insulating shield 4, passes through an exhaust hole 10 and a valve 11, and is discharged outside the system by a vacuum pump 12. At this time, a large amount of precipitates due to SiO adhere to the surfaces of the heater 3 and the heat insulating shield 4.

Here, the heater 3 and the heat insulating shield 4 are
Since it is made of graphite, it deteriorates due to the precipitation of SiO-induced substances, or it may be necessary to remove the precipitates after the operation is completed.
There has been a problem that a lot of manpower and time are required for reassembling.

The present invention is intended to solve the above-mentioned problems, and an object thereof is to prevent SiO-derived substances from precipitating on graphite parts and prevent deterioration of graphite parts due to precipitation of SiO-derived substances. In addition, the work of removing precipitates from graphite parts can be eliminated or extremely reduced,
Furthermore, the operating period can be greatly extended without disassembling / reassembling graphite parts, and since there are few precipitates on graphite parts, disassembly / reassembly is simplified and large The present invention is to provide a silicon single crystal pulling apparatus that can be made larger and the diameter of a pullable silicon single crystal rod can be increased.

[0011]

A silicon single crystal pulling apparatus of the present invention is a apparatus for pulling a silicon single crystal in an inert gas atmosphere by the Czochralski method, and a crucible for containing a silicon melt. A heater provided on the outer periphery of the crucible, a heat insulating shield provided on the outer periphery of the heater, an exterior material forming a pulling chamber for housing the crucible, and an inert gas introducing portion provided above the pulling chamber,
The heat shield has an inert gas exhaust portion provided on a bottom surface portion other than the bottom surface of the pulling chamber surrounded by the inner peripheral surface of the heat insulating shield, which is provided below the pulling chamber, and the heat insulating shield has the inside or the exterior material. An air passage is formed between the upper and lower ends of the air passage, and the opening is provided close to the opening edge of the crucible, and the lower end of the air passage is not open. It is characterized by being communicated with the active gas exhaust unit.

The present invention will now be described in more detail with reference to the drawings. FIG. 1 is an explanatory view showing a schematic configuration of a silicon single crystal pulling apparatus according to the present invention. In FIG. 1, 2 is a silicon melt, 1 is a crucible for containing the silicon melt 2, 3 is a heater provided on the outer periphery of the crucible 1, 6 is a pulling chamber, 14 is an exterior material forming the pulling chamber 6, 15 Is an inert gas inlet provided above the pulling chamber 6, 16 is an inert gas exhaust provided below the pulling chamber 6, and 4 is a heat insulating shield provided on the outer periphery of the heater 3.

The heat insulating shield 4 is formed of double walls, and the hollow portion formed between the double walls serves as a ventilation path 17. An opening 18 is formed at the upper end of the air passage 17, and the lower end of the air passage 6 communicates with the inert gas exhaust unit 16. As a result, a flow path from the opening 18 of the heat insulating shield 4 to the inert gas exhaust unit 16 via the ventilation path 17 is formed. The opening 18 of the heat insulating shield 4 is provided at a position close to the opening edge 19 of the crucible 1. By doing so, SiO generated from the silicon melt 2 in the crucible 1
Before being diffused to the surroundings, it is sucked into the ventilation passage 17 whose pressure is slightly reduced from the inside of the pulling chamber 6.
Contamination by O is prevented.

The inert gas exhaust unit 16 is composed of an exhaust hole 20, a vacuum pump 12 and a valve 11, and is provided with a pulling chamber 6
The pressure is controlled to be slightly lower than the internal pressure. As a result, an air flow from the pulling chamber 6 to the inert gas exhaust unit 16 is generated.

A seed crystal (not shown) is immersed in the silicon melt 2 housed in the crucible 1 made of quartz, and while the crucible 1 and the seed crystal are rotated, silicon is deposited on the seed crystal for crystal growth. Here, the silicon melt 2 in the crucible 1 causes thermal convection due to density unevenness due to temperature difference due to heating, and forced convection also occurs due to rotation of the crucible 1 and the silicon single crystal 5. Then, due to these convections, the silicon melt 2 rubs against the wall surface of the crucible 1 to dissolve the quartz crucible 1 and take in oxygen. Here, the pressure inside the pulling chamber 6 is reduced to 100 mbar or less, and an inert gas 7 such as argon gas is flown from above the pulling chamber 6.

The oxygen taken into the silicon melt 2 is
It becomes SiO and evaporates. The inert gas 7 introduced from above the pulling chamber 6 flows from the opening 18 formed at the upper end of the vent passage 17 of the heat insulating shield 4 formed of a double wall together with SiO in the pulling chamber 6 to the vent passage 17 Get in,
It is discharged from the inert gas exhaust unit 16.

[0017]

In the heat insulating shield 4, a ventilation passage 17 is formed inside or with the exterior material, an opening 18 is formed at an upper end portion of the ventilation passage 17, and a lower end portion of the ventilation passage 17 is inactive. It is in communication with the gas exhaust unit 16 and has an opening 18
Is provided in a position close to the opening edge 19 of the crucible 1, so that SiO generated from the silicon melt 2 in the crucible 1 is sucked into the ventilation passage 17 from the opening 18 before it is diffused to the surroundings. It will be. That is, the inert gas 7 and the silicon melt 2 introduced from above the pulling chamber 6
The SiO generated from the above becomes difficult to flow to a place other than the flow passage for exhaust, and it is difficult to contact the graphite part provided in the place other than the flow passage. Therefore, it is possible to prevent SiO entrained in the inert gas from depositing on each member in the pulling device such as a graphite component.

[0018]

EXAMPLES Next, the present invention will be described in more detail with reference to examples. Example 1 Using the single crystal pulling apparatus shown in FIG. 1, a silicon single crystal rod having a diameter of 4 inches and an axial orientation of <100> was pulled.
The inner diameter of the quartz crucible 1 is 14 inches, the atmospheric pressure in the pulling chamber 6 is 100 mbar, and the quartz crucible 1 is 8 rp.
m, the silicon single crystal 5 was pulled up while rotating the seed crystal in the opposite directions at 25 rpm. As the inert gas, argon gas was flown into the pulling chamber 6 at a flow rate of 110 Nl / min. Also, to compare the amount of SiO precipitation,
A graphite plate having a diameter of 100 mm and a thickness of 5 mm was left on A and B in FIG. Under these conditions, the pulling operation was performed for 69.67 hours, and the weight increase of the graphite plates A and B and the heater 3 in FIG. 1 was examined. It was found that the graphite plates A and B and the heater 3 did not increase in weight and SiO was not deposited. Moreover, when the oxygen concentration in the pulled up silicon single crystal was measured by the FT-IR method (Fourier transform infrared spectroscopy), it was found to be about 0.5 ppma lower than that in Comparative Example 1 below. Furthermore, defects (O
The SF density) was equal to or slightly less than that of Comparative Example 1, and no particular difference in carbon concentration was observed as compared with Comparative Example 1.

Comparative Example 1 A silicon single crystal was pulled in the same manner as in Example 1 except that the conventional silicon single crystal pulling apparatus as shown in FIG. 2 was used. When the weight increase of the graphite plates A and B and the heater 3 in FIG. 2 was examined by performing a pulling operation for 26.67 hours, the weight increase of the heater 3 was not found, but the graphite plate A increased by 46.4 mg, B showed an increase of 3.3 mg.

[0020]

As is apparent from the above description, according to the silicon single crystal pulling apparatus of the present invention, the heat insulating shield has the air passage formed inside or with the exterior material,
An opening is formed at the upper end of the ventilation passage, the lower end of the ventilation passage is connected to the inert gas exhaust portion, and the opening of the heat shield is provided at a position close to the opening edge of the crucible. Therefore, SiO generated from the silicon melt in the crucible is sucked from the opening before it diffuses to the surroundings, is discharged from the inert gas exhaust section through the ventilation passage, and is pulled inside the pulling device such as a graphite member. Of the SiO-derived substance is prevented from being deposited on each member, and deterioration due to the deposition of the SiO-derived substance is prevented, and the work of removing the deposit from each member in the pulling device is eliminated or extremely reduced. In addition, it is possible to significantly extend the period of operation without disassembling and reassembling the pulling device,
Moreover, since there are few members in which SiO-derived substances are deposited, the work of disassembly and reassembly is simplified, and it is possible to increase the size.
The diameter of the pullable silicon single stick can also be increased. And, such an advantage is possible while maintaining good quality of the pulled single crystal ingot.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a schematic configuration of a silicon single crystal pulling apparatus according to the present invention.

FIG. 2 is a vertical cross-sectional view showing a schematic configuration of a conventional silicon single crystal pulling apparatus.

[Explanation of symbols]

 1 Crucible 2 Silicon Melt 3 Heater 4 Heat Insulation Shield 5 Silicon Single Crystal 6 Pulling Chamber 7 Inert Gas 9a, 9b Gap 10 Exhaust Hole 11 Valve 12 Vacuum Pump 14 Exterior Material 15 Inert Gas Inlet 16 Inert Gas Exhaust 17 Ventilation passage 18 Opening 19 Opening edge 20 Exhaust hole

Front page continuation (72) Inventor Tadashi Niwayama 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Semiconductor Co., Ltd. Isobe factory (72) Inventor Tetsuhiro Oda 2--13-50, Kitafu, Takefu City, Fukui Prefecture Shinetsu Semiconductor Co., Ltd., Takefu Factory

Claims (2)

[Claims] 1. A device for pulling a silicon single crystal in an inert gas atmosphere by the Czochralski method, comprising a crucible for containing a silicon melt, a heater provided on the outer periphery of the crucible, and an outer periphery of the heater. A heat shield provided, an exterior material that forms a pulling chamber that houses the crucible, and an inert gas introduction portion that is provided above the pulling chamber,
The heat shield has an inert gas exhaust portion provided on a bottom surface portion other than the bottom surface of the pulling chamber surrounded by the inner peripheral surface of the heat insulating shield, which is provided below the pulling chamber, and the heat insulating shield has the inside or the exterior material. An air passage is formed between the upper and lower ends of the air passage, and the opening is provided close to the opening edge of the crucible, and the lower end of the air passage is not open. A silicon single crystal pulling apparatus characterized by being connected to an active gas exhaust unit. 2. An apparatus for pulling a silicon single crystal, wherein the heat insulating shield has a double wall, and the hollow portion of the double wall serves as a ventilation path.