Numerical investigations of laser-induced crystallization and stress development in phase changes of electroceramic materials

Barium-Strontium-Titanate, BST, in the stoichiometry Ba 0.7Sr0.3TiO3 to Ba0.5Sr 0.5TiO3 is been considered as a promising candidate to enter into the DRAM manufacturing technology. The incompatibility between the temperatures required to crystallize the ferro/para-electric layer into the required Perovskite phase and the thermal budget of underlying active circuitry rules out the application of conventional, quasi-stationary heat treatment of these new materials when integrating into the circuit fabrication process. Therefore, the research focuses on heating amorphous ceramic thin films by laser radiation with pulse durations in the ns regime to induce changes in their structural and electronic properties in the heated region only. To establish initial operating parameters for the laser-induced crystallization and to study the amorphous to crystalline phase transformation including stress formation a simulation program is developed. The model includes heat transfer, cry stallization and thermal respective phase transformation induced stress analysis.