Single-crystal – oriented-crystal – and epitaxy growth processes; – Processes of growth from liquid or supercritical state – Having pulling during growth
Patent
1999-12-09
2000-12-12
Utech, Benjamin L.
Single-crystal, oriented-crystal, and epitaxy growth processes;
Processes of growth from liquid or supercritical state
Having pulling during growth
117 14, 117 15, 117 35, C30B 1526
Patent
active
06159282&
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of pulling a single crystal and, more particularly, to a method of pulling a single crystal wherein a single crystal of silicon or the like is pulled from a melt of a material for forming a single crystal by a pulling method such as the Czochralski method (hereinafter, referred to as the CZ method).
BACKGROUND ART
At present, the majority of silicon single crystals used for manufacturing a substrate for forming a circuit component of a LSI (large scale integrated circuit) and the like have been pulled by the CZ method. FIG. 1 is a diagrammatic sectional view of a conventional apparatus for pulling a single crystal using the CZ method. In the figure, reference numeral 21 represents a crucible.
The crucible 21 comprises a bottomed cylindrical quartz crucible 21a and a bottomed cylindrical graphite crucible 21b fitted on the outer side of the quartz crucible 21a. The graphite crucible 21b is fitted in a graphite fitting part 28a. The crucible 21 and the fitting part 28a are supported with a support shaft 28 which rotates in the direction shown by the arrow A in the figure at a prescribed speed. A heater 22 of a resistance heating type and a heat insulating mold 27 arranged around the heater 22 are concentrically arranged around the crucible 21. The crucible 21 is charged with a melt 23 of a material for forming a crystal which is melted by the heater 22. On the central axis of the crucible 21, a pulling axis 24 made of a pulling rod or wire is suspended, and at the lower end thereof, a seed crystal 35 is held by a holder 34a. These parts are arranged within a water cooled type chamber 39 wherein pressure can be controlled, while an optical measuring means 19 is arranged above the crucible 21 outside the chamber 39.
In pulling a single crystal 36 using the above-mentioned apparatus for pulling a single crystal 30, the pressure in the chamber 39 is reduced and an inert gas is introduced into the chamber 39 so as to make an inert gas atmosphere under reduced pressure, which is maintained for a period of time. Then, the material for forming a crystal is melted by the heater 22.
While the pulling axis 24 is rotated on the same axis in the reverse direction of the support shaft 28 at a prescribed speed, the seed crystal 35 held by the holder 34a descends and is brought into contact with the melt 23, and the pulling of the single crystal 36 from the melt 23 is started. When the crystal is made to grow at the lower end portion of the seed crystal 35 as the pulling is carried out, the crystal is once narrowed down to have a prescribed diameter, leading to the formation of a neck 36a (hereinafter, referred to as the necking step).
After forming a shoulder 36b by making the neck 36a grow to have a prescribed diameter, a main body 36c having a uniform diameter and a prescribed length is formed. The diameter of the single crystal 36 is gradually decreased and the temperature of the whole single crystal 36 is gradually lowered, leading to the formation of an end-cone. Then, the single crystal 36 is separated from the melt 23. Here, in the above steps, the diameter of the single crystal 36 is measured by measuring luminance of the growth interface (fusion ring) on the surface of the melt 23 when the single crystal 36 is formed, using the optical measuring means 19, and is controlled on the basis of the results.
In the above conventional method for pulling a single crystal, the neck 36a is formed under the seed crystal 35 in order to exclude the dislocation induced by a thermal shock when the seed crystal 35 is brought into contact with the melt 23. Ordinarily, the neck 36a has a diameter of 3 mm or so and a length of 30 mm or so. In pulling a single crystal 36 having a diameter of about 6 inches and a weight of 80 kg or so, even the neck 36a having the above diameter can sufficiently support the pulled single crystal 36.
Recently, however, in order to manufacture a more highly integrated semiconductor device at a lower cost and more efficiently, the wafer has bee
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Champagne Donald L.
Sumitomo Metal Industries Ltd.
Utech Benjamin L.
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