JPH0616491A - Silicon single crystal pulling up device - Google Patents

Abstract

PURPOSE:To prevent the deposition of the material occurring in SiO in graphite parts and to prolong the period of using the device by providing an introducing part and discharging part for an inert gas in such a manner that the inert gaseous flow is formed above a pulling up chamber. CONSTITUTION:This silicon single crystal pulling up device by a Czochralski method consists of a crucible 1, a silicon melt 2, a heater 3, a pulling up chamber 6, an external body 14, the inert gas introducing part 15, the inert gas discharging part 16 and a heat insulating shield 4. The discharging part 16 is constituted of a discharging hole 20, a vacuum pump 12 and a valve 11 and is so controlled that the pressure therein is slightly lower than the gaseous pressure in the pulling up chamber. As a result, the gaseous flow from the pulling up chamber 6 to the discharging chamber 16 is generated. The SiO is evaporated by the force convection, etc., generated by rotation of the crucible 1 and the silicon single crystal 5. The pressure in the pulling up chamber 6 is reduced down to <=100mbarr and the inert gas 7 is run therein. The SiO diffusing above the pulling up chamber 6 is entrained in the above-mentioned inert gaseous flow and is discharged from the discharging part 16.

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 the 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, the inert gas 7 is melted. Through the gap 9a formed between the crucible 1 and the heater 3 and the gap 9b formed between the heater 3 and the heat insulating shield 4, the exhaust hole 10, the valve 11
Through the vacuum pump 12 is discharged to the outside of the system.
A large amount of deposits due to SiO will 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, an exterior body forming a pulling chamber for housing the crucible, an inert gas introducing portion provided above the pulling chamber, and a pulling chamber separated from the inert gas introducing portion. And an inert gas exhaust portion provided at an upper position.

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 body forming the pulling chamber 6, 15 Is an inert gas introducing portion provided above the pulling chamber 6, 16 is separated from the inert gas introducing portion 15, and the pulling chamber 6 is
An inert gas exhaust portion 4 provided above the heater 3 is a heat insulating shield provided on the outer circumference of the heater 3.

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 the uneven density due to the temperature difference due to heating, and forced convection due to the 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, and the crucible 1 made of quartz is rubbed.
Is dissolved and oxygen is taken in. Here, the inside of the pulling chamber 6 is 1
The pressure is reduced to 00 mbar or less, and an inert gas 7 such as argon gas is caused to flow from an inert gas inlet provided above the pulling chamber.

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 is discharged from the inert gas exhaust unit 16 together with the SiO in the pulling chamber 6.

[0016]

Since the inert gas introducing portion is provided above the pulling chamber, and the inert gas exhausting portion provided at a position above the pulling chamber is provided apart from the inert gas introducing portion, An inert gas flow from the inert gas introduction part to the inert gas exhaust part is formed above the pulling chamber, and
Since this air flow does not come into contact with a member that is susceptible to contamination in the pulling chamber, the SiO generated from the silicon melt in the crucible and diffused above the pulling chamber is accompanied by the above air flow, and the inert gas exhaust part More discharged. here,
Since SiO evaporates more gently than the silicon melt, and the cross-sectional area of the path leading to the upper part of the pulling chamber is very large,
The probability that SiO collides with the surface of the member in the pulling chamber by the time it reaches the upper part of the pulling chamber is very small, so that the precipitation of the SiO-derived substance on the graphite member in the pulling chamber is suppressed to a very low level.

[0017]

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. Further, in order to compare the deposition amount of SiO, graphite plates having a diameter of 100 mm and a thickness of 5 mm were left at 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. Further, when the oxygen concentration in the pulled up silicon single crystal was measured by the FT-IR method (Fourier transform infrared spectroscopy), it was about 0.5 ppma as compared with Comparative Example 1 below.
Turned out to be low. Further, the defects (OSF density) in the silicon single crystal were the same as or slightly less than those in Comparative Example 1, and the carbon concentration was not particularly different from that in 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.

[0019]

As is apparent from the above description, according to the silicon single crystal pulling apparatus of the present invention, the inert gas introducing section provided above the pulling chamber and the inert gas introducing section separated from each other. In addition, since it has an inert gas exhaust portion provided at a position above the pulling chamber, an air flow of the inert gas from the inert gas introducing portion to the inert gas exhaust portion is formed above the pulling chamber, and Since the air flow does not come into contact with the member in the pulling chamber where contamination is likely to occur, SiO generated from the silicon melt in the crucible and diffused above the pulling chamber is accompanied by the above-mentioned air flow and is discharged from the inert gas exhaust section. The SiO-derived substance is prevented from being deposited and deposited on each member in the pulling device such as the graphite member.
Deterioration due to the precipitation of the causative substance can be prevented, and the work of removing the precipitate from each member in the pulling device can be eliminated or extremely reduced, and without disassembling and reassembling the pulling device. The operating period can be greatly extended, and because there are few members that deposit SiO-derived substances, disassembly and reassembly work can be simplified and upsizing can be achieved. The diameter 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 Body 15 Inert Gas Introducing Section 16 Inert Gas Exhausting Section 20 Exhaust hole

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Namiyama 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Semiconductor Co., Ltd. Isobe factory (72) Inventor Tetsuhiro Oda 2-13, Kitafu, Takefu City, Fukui Prefecture No. 50 Shin-Etsu Semiconductor Co., Ltd., Takefu Factory

Claims (4)

[Claims] 1. A device for pulling a silicon single crystal in an inert gas atmosphere by the Czochralski method, which comprises a crucible for containing a silicon melt, a heater provided on the outer periphery of the crucible, and a crucible. An exterior body forming a pulling chamber, an inert gas introducing portion provided above the pulling chamber, and an inert gas exhaust portion provided at a position above the pulling chamber and separated from the inert gas introducing portion. A silicon single crystal pulling apparatus having. 2. The silicon single crystal pulling apparatus according to claim 1, wherein the inert gas introducing portion is provided in the center above the pulling chamber, and the inert gas exhausting portion is provided in a corner above the pulling chamber. . 3. The silicon single crystal pulling apparatus according to claim 2, wherein the inert gas introducing portion is provided in the pulling chamber, and the inert gas exhaust portion is provided at two or more places in the pulling chamber. 4. An inert gas exhaust part provided at two or more places in the pulling chamber is arranged at a substantially symmetrical position with respect to a central axis of the pulling chamber, and a plurality of pairs of the two inert gas exhaust parts are provided. It forms, The silicon single crystal pulling apparatus of Claim 3 characterized by the above-mentioned.