Ge-rich Ge-Sb-Te Phase-Change Thin Films Under the Light of Synchrotron Radiation— Crystallization and Thermomechanical Behavior

Phase Change Memory is a very promising non-volatile memory that is being considered by several companies for a wide range of applications (storage-class memory, in-memory computing, neuromorphic computing, eNVM for microcontrollers …). At STMicroelectronics a new Ge-rich Ge-Sb-Te alloy (GGST) has been developed with a crystallization temperature above 350°C [1] for addressing the specific needs of the automotive market where high operating temperatures are needed. To investigate the crystallization and mechanical behavior of these GGST alloys we use X-ray diffraction as a function of temperature during annealing. Capped thin films are heated <i>in situ</i> under nitrogen atmosphere on the DiffAbs beamline of SOLEIL synchrotron facility. The incident beam is monochromatic (18 keV) and the incidence is fixed. A bidimensional detector collects the diffraction pattern and is corrected and integrated [2] to yield a 1D diffraction pattern. The diffraction peaks are then fitted with a Voigt function [3] that allows extracting the integrated intensity, integral breadth and position of the Bragg peaks. These parameters allow following the crystallization kinetics and the thermomechanical behavior [4] of thin films as a function of various parameters: doping, film thickness (5 nm – 50 nm), nature of surrounding layers … In addition, we will show that thanks to the high flux and penetrating power of synchrotron X-rays patterned and metallized structures close to real products can be investigated. The results obtained from such in situ investigations bear important consequences for the understanding of the crystallization process in memory cells.<br/><br/><b>Acknowledgments:</b><br/>The authors gratefully acknowledge the SOLEIL Synchrotron for allocating beam time. P. Joly, is acknowledged for excellent technical support during the experimental campaign at SOLEIL Synchrotron on DiffAbs beamline. This research was supported by IPCEI/Nano 2022 program.<br/><br/><b>References:</b><br/>[1] P. Zuliani <i>et al.</i>, Solid State Electronics 111, 27 (2015).<br/>[2] C. Mocuta<i> et al.</i>, J. Appl. Crystallogr. 47, 482 (2014).<br/>[3] P. Hans <i>et al</i>., Phys. Satus Solidi RRL 2100658 (2022).<br/>[4] O. Thomas <i>et al</i>., Microelectronic Engineering 244, 11573 (2021).