Patent ID: 8673075
Filing Date: 2014-03-18
Classification: C30B,Y10T

Abstract:
1. A semiconductor crystal growth apparatus comprising: a crucible to hold melt; a crystal pull unit configured to pull a crystal from the crucible at a pull speed; a control unit including a memory to store data and instructions and a processing unit configured in response to the stored data and instructions to determine the pull speed and to produce control signals for the crystal pull unit, the control unit coupled with the crystal pull unit and configured to control the pull speed by applying the control signals to the crystal pull unit so that the pull speed is modulated about an average pull speed, by superimposing a periodic pull speed on the average pull speed, according to where v is the pull speed, v a temperature gradient estimation system configured to estimate thermal gradients in the crystal and the melt based in part on a response to the superimposed periodic pull speed.