JPH054358B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to the structure of a quartz crucible for improving the quality of semiconductor monocrystalline silicon rods pulled by the Czyochralski method, particularly for reducing the carbon content.

(Prior art and its problems) Semiconductor silicon single crystal rods are processed into wafers and used as silicon substrates for manufacturing semiconductor devices or semiconductor integrated circuit devices, but no matter how high-purity polycrystals are used, , the carbon content of the substrate increases and can reach 1 ppma. Such substrates are not suitable for the above applications. For example, the content
When semiconductor devices or semiconductor integrated circuit devices are manufactured using wafers of approximately 0.5 ppma, the withstand voltage at the PN junction decreases, and leakage current may occur between electrodes in MOS structure devices.
Since the carbon content must be kept to a minimum, various measures have been taken, but none of them have been able to achieve sufficient effects, as described below.

The apparatus shown in FIG. 2 is a conventional monocrystalline silicon rod manufacturing apparatus using the Czyochralski method, in which polycrystalline silicon is charged as a raw material in a quartz crucible 1 and heated and melted by a heater 2. The crucible 1 is fitted into a graphite susceptor 3, supported at the center of the bottom by a rotating shaft 4, and has a heat shield 5.
It is housed in the chamber 6 along with the Atmospheric gas is introduced through the supply port 7 and exhausted through the exhaust port 8 . After sufficiently melting the polycrystalline silicon by heating with a heater, the seed crystal 10 held at the lower end of the pulling shaft 9 is immersed in the melt and pulled up to form a single crystal 1.
1 is cultivated.

However, in this method, oxygen or moisture gradually released from the graphite material in the chamber reacts with the heater to produce carbon oxide gas, and contact between the quartz crucible and the susceptor produces carbon monoxide gas, which flows back. This contaminates the silicon melt 12.

To avoid this, if the upper edge 13 of the quartz crucible 1 is made higher than the upper edge 14 of the susceptor, the upper edge of the crucible will move away from the heater, the temperature will drop, and the silicon monoxide deposited here will fall into the silicon melt 12. This disturbs single crystal growth. A method of coating the graphite material inside the chamber with silicon nitride has also been proposed, but although it is effective in preventing contamination, it is too expensive and uneconomical. Furthermore, a method of providing a shielding device in the form of a donut-shaped disk on the upper edge of the heat shield 5 was considered, but it was not possible to effectively prevent the incorporation of carbon into the silicon melt.

(Means for Solving the Problems) As a result of various studies to solve the above problems, the inventor of the present invention has found that the single crystallization rate can be reduced by slightly changing the shape of the upper edge of the quartz crucible. We succeeded in producing single crystal silicon with low carbon content, and this was achieved by using a quartz crucible that is used to pull semiconductor single crystal silicon rods using the Czyochralski method.
This is a flanged quartz crucible characterized by having a flange inclined outward at 30° to 120° and having a width of 5 to 50 mm on the upper edge of the cylindrical side wall.

FIG. 1 shows an embodiment of a single-crystal silicon rod pulling device using the Czyochralski method using the flanged quartz crucible of the present invention.

Since the collar 15 only needs to cover at least the upper edge of the graphite susceptor, a width of 5 mm is sufficient, but more preferably it is complete if it also covers the graphite heater. In order to further the objective of the present invention of avoiding contamination of the silicon single crystal, it is preferable that the width of the collar 15 is further widened, but since it cannot be widened beyond the heat shield 5 surrounding the heater 2, There is a limit. For this reason, the upper limit is approximately
50mm is selected. Further, the inclination angle θ with respect to the vertical line directed upward of the tsuba can be increased from 0° to 120°. Furthermore, the quartz crucible of the present invention is effective in preventing silicon monoxide from falling onto the surface of the silicon melt.

(Function) As is clear from Fig. 1, the flange 15 provided facing outward on the upper edge of the quartz crucible covers the graphite susceptor and graphite heater, so that carbon monoxide or carbon dioxide generated from them is It is not easy to reach quartz crucibles.
This is because, in order for the carbon oxide to come into contact with the silicon melt 12 in the quartz crucible, it must flow back through the quartz collar surface and the boundary layer region of the atmospheric gas by diffusion.

(Example) In the apparatus for pulling a single crystal silicon rod using the Czyochralski method shown in FIG.
Charge and melt 50 kg of polycrystalline silicon in a tube (equipped with a 90° flange), and while keeping the internal pressure of argon gas at 50 mb in an undoped state, let it flow at a flow rate of 50 l/min, and the diameter will be adjusted in the pulling direction (100). Five batches of 160 mm single crystal silicon rods were pulled up. Wafers were cut out from the tail side of these single crystal rods at a solidification rate of 85% and measured using an infrared absorption carbon concentration measuring device. No substitutional carbon was detected (the detectable amount of carbon with this device was 0.01ppma).
That's all).

(Comparative Example) When a single crystal was pulled under the same conditions as in the example except that a conventional quartz crucible without a collar was used, an average of 0.15 ppma of substitutional carbon was detected.

(Effects of the Invention) As described above, the quartz crucible of the present invention can suppress the carbon content of pulled single crystal silicon to 0.01 ppma or less, and is an economical and industrially useful invention.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a single crystal silicon rod pulling device using the Czyochralski method using the flanged quartz crucible of the present invention. A vertical cross-sectional view of a silicon rod pulling device is shown. 1... Quartz crucible, 2... Heater, 3... Susceptor, 4... Rotating shaft, 5... Heat shield, 6... Chamber, 7... Supply port, 8... Discharge port, 9... Pulling shaft, 10... Seed crystal, 11... Single Crystal, 12...melt,
13... Upper edge of crucible, 14... Upper edge of susceptor, 15
...Tsuba, θ...Tilt angle.

Claims (1)

[Claims] 1. In a quartz crucible used for pulling semiconductor single crystal silicon rods using the Czyochralski method, a flange with a width of 5 to 50 mm that is inclined outward from 30° to 120° from the vertical upward direction is attached to the upper edge of the cylindrical side wall. A quartz crucible with a flange.