Single crystal and semiconductor wafer and apparatus and method for producing a single crystal

Abstract

The disclosure relates to an apparatus and a method for producing a single crystal of semiconductor material. The apparatus comprises a chamber and a crucible which is arranged in the chamber and is enclosed by a crucible heater, a radiation shield for shielding a growing single crystal and thermal insulation between the crucible heater and an inner wall of the chamber. The apparatus may include a resilient seal which seals a gap between the inner wall and the thermal insulation and forms an obstacle for the transport of gaseous iron carbonyls to the single crystal. The disclosure also relates to a method for producing a single crystal of semiconductor material by using the apparatus, the single crystal which is produced and a semiconductor wafer cut therefrom. The single crystal and the semiconductor wafer are distinguished by an edge region, which extends from the circumference to a distance of up to R-5 mm radially into the single crystal or the semiconductor wafer and has an iron concentration, wherein the iron concentration in the edge region is less than 1*109 atoms/cm3.

Description

Claims

1. An apparatus for producing a single crystal of semiconductor material, the apparatus comprising: a chamber defining an inner wall;a crucible disposed in the chamber;a crucible heater substantially surrounding the crucible;a radiation shield configured to shield the single crystal;thermal insulation disposed between the crucible heater and the inner wall of the chamber; anda resilient seal that substantially seals the gap between the inner wall and the thermal insulation.

2. The apparatus of claim 1, wherein the seal forms an obstacle against a transport of gaseous iron carbonyls to the single crystal and the seal reduces the transport of the gaseous iron carbonyls to the single crystal by at least about 50%.

3. The apparatus of claim 1, wherein the resilient seal is substantially ring-shaped.

4. The apparatus of claim 1 wherein the resilient seal allows for a thermal expansion of the thermal insulation.

5. The apparatus of claim 1, wherein the seal includes a graphite felt.

6. The apparatus of claim 5 wherein the graphite felt includes carbon fibers.

7. The apparatus of claim 1 further comprising an active cooling system for cooling the single crystal.

8. The apparatus of claim 1 further comprising a ceramic coating on the inner wall of the chamber.

9. A seal for use in an apparatus for producing a single crystal of semiconductor material, the apparatus including a chamber defining an inner wall, a crucible disposed in the chamber, a crucible heater substantially surrounding the crucible, a radiation shield for shielding the single crystal, and thermal insulation disposed between the crucible heater and the inner wall of the chamber, the thermal insulation and the inner wall defining a gap therebetween, the seal comprising: a resilient material that seals the gap between the inner wall and the thermal insulation, the resilient material providing a substantial obstacle against transport of gaseous iron carbonyls to the single crystal.

10. A system for reducing transport of gaseous iron carbonyls to a single crystal in a crystal-growing apparatus, the apparatus including a chamber defining an inner wall, a crucible disposed in the chamber, a crucible heater substantially surrounding the crucible, a radiation shield for shielding the single crystal, and thermal insulation disposed between the crucible heater and the inner wall of the chamber, the thermal insulation and the inner wall defining a gap therebetween, the system comprising: a resilient seal disposed in the gap between the inner wall and the thermal insulation; andan active cooling system disposed adjacent the single crystal to cool the single crystal during growth.

11. A method for producing a single crystal of semiconductor material by pulling the single crystal from a crucible in a chamber that defines an inner wall, wherein the crucible is substantially surrounded by a crucible heater, and further wherein a thermal insulation is disposed within the chamber and the thermal insulation and the inner wall define a gap therebetween, the method comprising the steps of: substantially sealing the gap with a resilient seal to form an obstacle against transport of gaseous iron carbonyls to the single crystal.

12. The method of claim 11, wherein the transport of gaseous iron carbonyls to the single crystal is reduced by at least about 50%.

13. The method of claim 11 further comprising a step of actively cooling the single crystal during growth.

14. The method of claim 11, further comprising a step of coating at least a substantial portion of the inner wall of the chamber with a ceramic material.

15. The method of claim 14 wherein the ceramic material includes aluminum oxide.

16. The method of claim 11, further comprising a step of removing iron deposited within the chamber.

17. A single crystal of semiconductor material having an iron concentration, the single crystal comprising a section of substantially cylindrical shape defining a circumference, a radius (R) and an edge region extending from the circumference to a distance of R-5 mm radially into the single crystal, wherein the iron concentration in the edge region is less than 1*109 atoms/cm3.

18. A semiconductor wafer having an iron concentration and defining a circumference, a radius (R) and an edge region extending from the circumference to a distance of R-5 mm radially into the semiconductor wafer, wherein the iron concentration in the edge region is less than 1*109 atoms/cm3.