Application of UV-Raman Spectroscopy for Characterization of the Physical Crystal Structure Following Flash Anneal of an Ultrashallow Implanted Layer

Abstract

Ultraviolet (UV) Raman spectroscopy provides new information on crystal structure and changes in structure with depth, not provided by conventional techniques. Characterization of the recrystallization process in ultrashallow B- or -implanted layers with preamorphization implantation of Ge on silicon was performed by nondestructive Raman spectroscopy utilizing multiwavelength UV excitation. To recrystallize damaged layers after ion implantation, a rapid annealing process was carried out in a millisecond flash anneal system. By making use of the shallow penetration depths of UV light in silicon, we can distinguish Raman signals of single-crystalline, deficiently recrystallized, as well as amorphous silicon, and thereby characterize the ultrashallow region at depths of several nanometers from the surface. Following the annealing, a single-crystalline lattice image was observed for a recrystallized layer using transmission electron microscopy. However, an intense Raman peak associated with deficiently recrystallized silicon that is spectroscopically equivalent to polycrystalline silicon was detected from the recrystallized layer. The deterioration is presumably correlated with the insufficient activation of B atoms in the recrystallized layer from measurements using the combination of secondary ion mass spectroscopy and spreading resistance profiles. Ultraviolet Raman spectroscopy is a very powerful, nondestructive tool to characterize the physical structure of the ultrashallow junction formation.