Computer-Controlled Economical and Reliable Tail-Off of Czochralski Silicon Crystal Growth
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
A novel method is provided for tail-off in the Czochralski silicon crystal growth, which is reproducible, reliable and economical in terms of crystal growth time and silicon material savings. Fig. 1 illustrates schematically a crystal grown using a new tail-off. The diameter of the growing crystal 1 is increased, in contrast to the crystal 1 of Fig. 2, where the diameter of the crystal is decreased. Fig. 2 represents typical tail-off being used in the industry. The diameter of crystal 1 of Fig. 1 is increased in a programmed way, by using a computer closed-loop control in conjunction with the diameter sensor, such as an optical pyrometer, TV camera or linear array of photodiodes. In an actual crystal growth of 128 mm diameter crystal, the diameter will be increased from 128 mm to 148 mm in 25-30 minutes.