Handbook of Silicon Based MEMS Materials and Technologies

2.3. Issues of Crystal Growth

In the following sections, diameter control, doping, and HZ lifetime are discussed.

2.3.1. Diameter Control

There is a clear-cut balance between the growth rate of the crystal and thermal gradients on both sides of the freezing interface. The growing crystal needs to be cooled, mainly through radiation, and to some extent also by the purge gas flow. Near the freezing interface, the heat flux density can be taken to be equal to the magnitude of thermal gradient times thermal conductivity, on both sides of the interface. However, the solidification process releases heat at a rate that is equal to the speed of crystallization times latent heat. In a balanced situation, the external pull speed of the crystal is equal ...