Advanced Thermal Control System for a Programmable Multizone Crystal Growth Furnace

A programmable, 24 independent-zone, computer-controlled furnace and control system have been developed for control of the thermal environment and process during crystal growth. The furnace and control system were designed to achieve capabilities which are beyond the state-of- the-art for crystal growth furnaces and control systems. New control system hardware, software, and power conversion techniques were developed to provide precise, accurate thermal control. New user interface software was developed to provide flexibility and ease of use for setting the crystal growth process steps and operating parameters and monitoring the crystal growth process progress. A data acquisition system was developed to provide in-depth evaluation of system performance during development and for use by crystal growth scientists developing new advanced crystal growth techniques. The system has demonstrated: extremely precise temperature control (±0.3°C) for all 24 zones during crystal growth at temperatures up to 1250°C; thermal reconfiguration and thermal profile movement in the furnace using control software; unique power conditioning and control system; and a capability for detailed flexible programming of process steps. The crystal growth furnace, control system, user interface, and thermal performance are presented herein.