Method of manufacturing semiconductor devices and semiconductor device containing oxygen-related thermal donors
A method of manufacturing a semiconductor device includes determining information that indicates an extrinsic dopant concentration and an intrinsic oxygen concentration in a semiconductor wafer. On the basis of information about the extrinsic dopant concentration and the intrinsic oxygen concentration as well as information about a generation rate or a dissociation rate of oxygen-related thermal donors in the semiconductor wafer, a process temperature gradient is determined for generating or dissociating oxygen-related thermal donors to compensate for a difference between a target dopant concentration and the extrinsic dopant concentration.
1. A method of manufacturing a semiconductor device, the method comprising
determining information indicating an extrinsic dopant concentration and an intrinsic oxygen concentration in a semiconductor wafer;
determining, on the basis of information about the extrinsic dopant concentration and the intrinsic oxygen concentration as well as a generation rate or a dissociation rate of oxygen-related thermal donors in the semiconductor wafer, a process temperature gradient for generating or dissociating oxygen-related thermal donors to compensate for a difference between a target donor concentration and the extrinsic dopant concentration, wherein the target donor concentration is greater than an extrinsic donor concentration; and
subjecting the semiconductor wafer to a main heat treatment that applies the process temperature gradient.
2. The method of claim 1 , wherein
determining the intrinsic oxygen concentration comprises measuring the intrinsic oxygen content after a heat treatment dissociating oxygen-related thermal donors and before heating the semiconductor wafer to a temperature beyond 350° C.
3. The method of claim 1 , wherein
determining the extrinsic dopant concentration comprises dissociating oxygen-related donors by heating the semiconductor wafer up to a temperature higher 480° C. and measuring the extrinsic dopant concentration after dissociating the oxygen-related thermal donors and before heating the semiconductor wafer to a temperature beyond 350° C.
4. The method of claim 1 , wherein
determining the extrinsic dopant concentration and the intrinsic oxygen concentration comprises measuring a first total dopant concentration, then heating the semiconductor wafer to a temperature higher 350° C., measuring a second total dopant concentration after the heating, and determining the extrinsic dopant concentration and the intrinsic oxygen concentration on the basis of a difference between the first and second total dopant concentrations and parameters of the heating.
5. The method of claim 1 , further comprising
measuring a first total dopant concentration and determining the process temperature gradient on the basis of a difference between the first total dopant concentration and the extrinsic dopant concentration.
6. The method of claim 1 , wherein
the process temperature gradient is determined on the basis of the generation rate of oxygen-related thermal donors in the semiconductor wafer.
7. The method of claim 6 , further comprising
dissociating oxygen-related thermal donors in an auxiliary heating process before subjecting the semiconductor wafer to a main heat treatment applying the process temperature gradient.
8. The method of claim 1 , wherein
the process temperature gradient is determined on the basis of a dissociation rate of oxygen-related thermal donors in the semiconductor wafer.
9. The method of claim 8 , further comprising
generating a maximum concentration of oxygen-related thermal donors in an auxiliary heating process before subjecting the semiconductor wafer to a main heat treatment applying the process temperature gradient.
10. The method of claim 1 , wherein
the process temperature gradient is an isothermal process given by a constant process temperature and a process time for which the process temperature is applied.
11. The method of claim 1 , further comprising
forming an interlayer dielectric at a front side of the semiconductor wafer before subjecting the semiconductor wafer to the main heat treatment.
12. The method of claim 1 , further comprising
forming a plurality of separated semiconductor dies from the semiconductor wafer after subjecting the semiconductor wafer to the main heat treatment.
13. The method of claim 1 , wherein
after the main heat treatment at least 25% of the donors in the semiconductor wafer are oxygen-related thermal donors.
14. The method of claim 1 , further comprising
forming transistor cells in the semiconductor wafer.
15. The method of claim 1 , wherein
the intrinsic oxygen concentration is in a range from 2E17 cm −3 to 6E17 cm −3 .
16. The method of claim 1 , further comprising
implanting, before generating the oxygen-related donors, protons to form a field stop layer in the semiconductor wafer.
17. The method of claim 16 , wherein
a main heat treatment that applies the process temperature gradient in addition activates the implanted protons of the field stop layer.