Monitoring Diameter Variation and Diameter Control Using Laser Beam and Image Processing in Czochralski Crystal Growth
Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
During conventional Czochralski (CZ) silicon crystal growth, an optical pyrometer is generally utilized as the sensor for controlling the crystal diameter. It activates temperature and crystal pull rate control loops. The pyrometer is typically focused at the meniscus/melt boundary region to monitor crystal diameter variation. However, the output of the pyrometer does not indicate the true instantaneous change of the diameter. In fact, it lags in time which is detrimental for VLSI crystal growth. This erroneous sensing of diameter change was tolerable for previous generation equipment, but is not acceptable for equipment required to grow silicon for high quality wafer products.