JPS63319288A - Flanged quartz crucible - Google Patents

Abstract

PURPOSE:To control the carbon content in a pulled-up single crystal Si to an extremely small value and to obtain the title crucible for pulling up a high- quality semiconductor single crystal Si rod by providing a flange inclined beyond a specified angle range from the vertical direction and having a specified width on the upper edge of a quartz crucible. CONSTITUTION:In the quartz crucible 1 to be used at the time of pulling up a semiconductor single crystal Si rod 11 by the Czochralski method, a flange 15 inclined outward at an angle of 30-120 deg. to the vertical direction and having 5-50mm width is provided on the upper edge of a cylindrical side wall. As a result, a graphite susceptor 3 and a graphite heater 2 are covered by the flange 15, and hence the CO or CO2 generated therefrom hardly reach the crucible 1. Consequently, the carbon content in the single crystal Si rod pulled up with the use of the flanged quartz crucible can be controlled to <=0.01ppm.

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 single crystal silicon rods pulled by the Czochralski 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 can be high and reach up to 1 ppma. Such substrates are not suitable for the above applications. For example, when semiconductor devices or semiconductor integrated circuit devices are manufactured using wafers with a content of about 0.5 Ppma, the withstand voltage at the PN junction decreases, and leakage current may occur between electrodes in MO8 structure devices. Since the carbon content must be kept to a minimum, various measures have been taken, but none of them have been sufficiently effective as described below.

The apparatus shown in FIG. 2 is a conventional single crystal silicon rod manufacturing apparatus using the Czochralski 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, the center of the bottom is supported by a rotating shaft 4, and the crucible 1 is housed in a chamber 6 together with a heat shield 5. Atmospheric gas is introduced from the supply lower and discharged from the exhaust port 8. After sufficiently melting the polycrystalline silicon by heating with a heater, the seed crystal 10 held between the lower end of the pulling shaft 9 is
When it is immersed in a melt and pulled up, a single crystal 11 is grown.

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. The silicon melt 12 is contaminated.

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 in 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 donut-shaped disk shield on the upper edge of the heat shield 5 was considered, but it was not possible to effectively prevent carbon from entering 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. They succeeded in producing single crystal silicon with low carbon content, and this was done in a quartz crucible used for pulling semiconductor single crystal silicon rods using the Czochralski method, from 30' to 120' from vertically upward. Tilt outward, width 5
This quartz crucible is characterized in that a flange of ~50III11 is provided on the upper edge of the cylindrical side wall.

FIG. 1 shows an embodiment of a single-crystal silicon rod pulling device using the Czochralski 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 m is sufficient, but it is more preferable that 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 50m.
m is selected. Further, the inclination angle θ with respect to the vertical line directed upward of the tsuba can be increased from 30° to 1206°. 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 collar 15 provided outward on the upper edge of the quartz crucible covers the graphite susceptor and the graph eye 1 to the heater, so carbon monoxide or carbon dioxide is generated from these. It is not easy to reach the quartz crucible. 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 Czochralski method shown in FIG.
an, width 50mm in a crucible of height 40an, O'.

= 900 tsuba attached) with silicon polycrystalline lump 5
Charge and melt 01Lg, and undope Al-4.
= While maintaining the internal pressure of 50 mb, Bong gas was flowed in at a flow rate of 50 Q/min, and 5 batches of single crystal silicon rods with a diameter of 160 m were pulled in the pulling direction (100). A wafer is cut from a position on the tail side of these single crystal rods where the assimilation rate is 85%,
When measured with an infrared absorption type carbon concentration meter, no substitutional carbon was detected (the amount of carbon that can be detected by this device is more than o, otppma).

(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, the average yield was 0.15pp.
Substituted carbon of ma 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 drawings]

Fig. 1 is a vertical cross-sectional view of a single crystal silicon rod pulling device using the Czochralski method using the flanged quartz crucible of the present invention, and Fig. 2 is a longitudinal cross-sectional view of a single crystal silicon rod pulling device using the Czochralski method using a conventional quartz crucible. A vertical cross-sectional view of the 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... Type Crystal, 11... Single crystal,
12... Melt liquid, 13... Upper edge of crucible,
14... Upper edge of susceptor, 15... Tsuba,
θ...Tilt angle. Copper 1 figure

Claims (1)

[Claims] In a quartz crucible used to pull a semiconductor single crystal silicon rod using the Czochralski method, the
A flange-equipped quartz crucible characterized in that a flange is provided on the upper edge of a cylindrical side wall, tilting outward at 120° and having a width of 5 to 50 mm.