NEW APPROACHES TO AUTOMATED CONTROL SYSTEM DESIGN FOR CZ SINGLE CRYSTALS GROWTH WITH DIAMETER 200-300 MM

摘要

Production of the modern extra-large and sophisticated integral schemes demands strict structural perfection of silicon single crystals grown by Czochralski pulling method. Possibility to growing ingot diameter increasing and realization of visible opportunities to obtain electro- physical parameters stability determine this method implementation. Modem integral schemes require single crystal Si with low concentration of microdefects and with stated oxygen concentration as well as dislocation-free. The crystals under investigation presented two kinds of microdefects different in both, concentration and size. A-defects are the microdefects of large size inside an ingot or a wafer. B-defects are the microdefects of smaller size distributing through the crystal up to the crystal surface. Pulling speed Vs plays essential role in point defects condensation in grown Si single crystal. Pulling speed causes changes in grown Si single crystal temperatures. As a result of that there is no time for defects to undergo hardening thus forming microdefects A, A′, B, α types. The production of such material is impossible without modern control systems implementation necessary for single crystal growth using mathematical models of physical processes based on Czochralski method. As stated in [3], the choice of methods of modeling and single crystal growth technological process optimization is determined by certain peculiarities of this process: great number of parameters, including uncontrolled ones; wide ranges of controlled parameters variations; stochastic variability of environment; high level noise fields.