Method for pulling a single crystal composed of silicon with a section having a diameter that remains constant
View Patent ↗Single crystal composed of silicon with a section having a diameter that remains constant, are pulled by a method wherein the single crystal is pulled with a predefined pulling rate v p having the units [mm/min]; and the diameter of the single crystal in the section having a diameter that remains constant is regulated to the predefined diameter by regulating the heating power of a first heating source which supplies heat to the single crystal and to a region of the melt that adjoins the single crystal and is arranged above the melt, such that diameter fluctuations are corrected with a period duration T that is not longer than (2·18 mm)/v p .
1. A method for pulling a single crystal comprising silicon with a section having a diameter that remains constant, by crystallizing silicon from a melt of silicon contained in a crucible, comprising
providing a first heating source which supplies heat to the single crystal and to a region of the melt that adjoins the single crystal, the first heating source being arranged above the melt;
providing a second heating source which is arranged around the crucible;
pulling the single crystal with a predefined desired pulling rate v p having the units [mm/min], wherein a predefined curve for v p , a predefined curve for the heating power of the first heating source, and a predefined curve for the heating power of the second heating source, for a disturbance-free case are chosen such that the quotient v/G of the crystallization rate v and the axial temperature gradient G at the phase boundary between the growing single crystal and the melt corresponds to a critical value at which neither vacancies nor silicon interstitials are formed in excess; and
regulating the diameter of the single crystal in the section having a diameter that remains constant to a predefined diameter by means of regulating the heating power of the first heating source, such that diameter fluctuations are corrected with a period duration T that is not longer than (2·18 mm)/v p , wherein the heating power of the second heating source is used as a manipulated variable of a downstream regulation for bringing back deviations of the heating power of the first heating source from the predefined curve for the heating power of the first heating source, if the deviations persist over a long period of time.
2. The method of claim 1 , wherein the first heating source is positioned above a melt surface and within a heat shield positioned between an inner wall of the crucible and the single crystal.
3. The method of claim 1 , wherein a bottom surface of the first heating source is from 30 to 70 mm above the surface of the silicon melt.
4. The method of claim 1 , wherein a distance d between a side surface of the single crystal and an inner surface of the first heating source is from 10 to 50 mm.