Procedure for in-situ determination of thermal gradients at the crystal growth front

A method for growing a semiconductor crystal, the method comprising:

• pulling the semiconductor crystal from a melt at a pull speed;
• modulating the pull speed by superimposing a periodic pull speed on an average speed, the average speed including a target pull speed plus a corrective speed;
• detecting a response to modulation of the periodic pull speed as a change in diameter of the crystal;
• and
• based on the change in diameter of the crystal, determining thermal gradients for a crystal growth front in the melt and in the crystal.

A method for growing a semiconductor crystal, the method comprising:

• pulling the semiconductor crystal from a melt at a pull speed;
• modulating the pull speed by superimposing a periodic pull speed on an average speed, the average speed including a target pull speed plus a corrective speed;
• detecting a response to modulation of the periodic pull speed as a change in meniscus height in the melt deduced from detected diameter modulation;
• and
• based on the change in meniscus height, determining thermal gradients for a crystal growth front in the melt and in the crystal.

A semiconductor crystal growth method comprising:

• generating a nominal pull speed signal;
• in response to the nominal pull speed signal, pulling a crystal from melt in a crucible at a nominal pull speed;
• measuring a diameter of the crystal;
• based on the measured diameter, generating a pull speed correction signal and combining the pull speed correction signal with the nominal pull speed signal;
• superimposing the nominal pull speed with a periodic signal of predetermined frequency;
• estimating temperature gradients in the crystal and the melt based in part on response to the superimposed periodic signal of predetermined frequency;
• and
• correcting the temperature gradient in the crystal by adjusting a crucible lift signal.