Method for pulling a silicon single crystal
View Patent ↗The invention relates to a method for pulling a silicon single crystal from a melt which is contained in a crucible, comprising immersion of a seed crystal into the melt; crystallization of the single crystal on the seed crystal by raising the seed crystal from the melt with a crystal pull speed; widening the diameter of the single crystal to a setpoint diameter in a conical section, comprising control of the crystal pull speed in such a way as to induce a curvature inversion of a growth front of the single crystal in the conical section.
1. A method for pulling a silicon single crystal from a silicon-containing melt which is contained in a crucible, comprising:
immersing a seed crystal into the melt;
crystallizing a single crystal on the seed crystal by raising the seed crystal from the melt with a crystal pull speed;
widening the diameter of the single crystal to a setpoint diameter in a conical section, wherein
the crystal pull speed is controlled in such a way as to induce a curvature inversion of a growth front of the single crystal in the conical section.
2. The method of claim 1 , comprising:
reducing the crystal pull speed from an initial speed to a lower crystal pull speed which is at least 40% less than the initial speed, and increasing the crystal pull speed from the lower crystal pull speed to a substantially constant final speed with which the seed crystal is raised until the setpoint diameter is reached.
3. The method of claim 2 , wherein the final speed is less than the initial speed.
4. The method of claim 2 , wherein the seed crystal is not raised with the lower crystal pull speed until the diameter of the conical section has reached at least 50% of the setpoint diameter.
5. The method of claim 3 , wherein the seed crystal is not raised with the lower crystal pull speed until the diameter of the conical section has reached at least 50% of the setpoint diameter.
6. The method of claim 1 , wherein an apex angle α of not less than 60° and not more than 90° is imparted to the conical section.
7. The method of claim 2 , wherein an apex angle α of not less than 60° and not more than 90° is imparted to the conical section.
8. The method of claim 3 , wherein an apex angle α of not less than 60° and not more than 90° is imparted to the conical section.
9. The method of claim 4 , wherein an apex angle α of not less than 60° and not more than 90° is imparted to the conical section.
10. The method of claim 5 , wherein an apex angle α of not less than 60° and not more than 90° is imparted to the conical section.
11. The method of claim 1 , wherein the external angle β at the transition from the conical section to the cylindrical section is not less than 5° and not more than 25°.
12. The method of claim 2 , wherein the external angle β at the transition from the conical section to the cylindrical section is not less than 5° and not more than 25°.
13. The method of claim 3 , wherein the external angle β at the transition from the conical section to the cylindrical section is not less than 5° and not more than 25°.
14. The method of claim 4 , wherein the external angle β at the transition from the conical section to the cylindrical section is not less than 5° and not more than 25°.
15. A silicon single crystal, produced by the method of claim 1 .