Crystal pulling apparatus having means for maintaining liquid solid crystal interface at a constant temperature

Abstract

Abstract APPARATUS FOR GROWING CRYSTALS COMPRISES A CRUCIBLE FOR HOLDING MOLTEN RAW MATERIAL TO BE GROWN INTO A CRYSTAL, MEANS INCLUDING A SHAFT FOR PLACING A SEED CRYSTAL IN THE MOLTEN RAW MATERIAL TO PROMOTE CRYSTAL GROWTH, TEMPERATURE SENSING MEANS INCLUDIG A MOVABLE THERMOCOUPLE FOR MEASURING THE TEMPERATURE OF THE BOUNDARY INTERFACE EXISTING BETWEEN THE GROWN CRYSTAL AND THE MOLTEN RAW MATERIAL AND PROVIDING A CORRESPONDING TEMPERATURE OUTPUT SIGNAL, AND TEMPERATURE REGULATING MEANS RECEPTIVE OF THE TEMPERATURE OUTPUT SIGNAL FOR COMPARING SAME WITH A REFERENCE SIGNAL REPRESENTATIVE OF THE DESIRED TEMPERATURE WHICH SHOULD BE MAINTAINED AT THE BOUNDARY INTERFACE. THE TEMPERATURE REGULATING MEANS COMPRISES A DIFFERENTIAL AMPLIFER FOR COMPARING THE TWO SIGNALS AND DEVELOPING A DIFFERENCE SIGNAL WHICH IS APPLIED TO A CONTROLLED POWER SOURCE FOR CONTROLLING THE ENERGIZATION OF HEATING ELECTRODES OF A HEATER. IN ORDER TO STABILIZE THE TEMPERATURE AT THE BOUNDARY INTERFACE, THE THERMOCOUPLE IS MOUNTED FOR MOVEMENT INTEGRALLY WITH THE HEATER AND IN SYNCHRONIZATION WITH THE LOWERING MOVEMENT OF THE BOUNDARY INTERFACE AND ACTUATING MEANS IS PROVIDED FOR EFFECTING MOVEMENT OF BOTH THE THERMOCOUPLE AND HEATER IN ACCORDANCE WITH THE LOWERING RATE OF THE BOUNDARY INTERFACE TO MAINTAIN THE THERMOCOUPLE AT A CONSTANTLY SPACED-APART DISTANCE FROM THE BOUNDARY INTERFACE THEREBY PROVIDING A MORE ACCURATE TEMPERATURE SENSING FUNCTION AND RESULTING IN A MORE STABILIZED CRYSTAL GROWTH.

Inventors

• 👤 Seiya Higashi
• 👤 Kenro Kobayashi

Bibliographic Details