Progress in the physical modeling of carrier illumination

Abstract

Carrier illumination is an optical, fast, and nondestructive technique for an ultrashallow complementary metal oxide semiconductor structure characterization based on the measurement of differential probe laser reflectivity changes, which originate from refractive index variations induced by excess carriers generated by a second modulated pump laser. By changing the pump laser power it is possible to influence the depth of the main internal reflection and thus to sense the shape of the underlying electrically active profile. The extraction of the latter is, however, critically dependent on our in-depth physical understanding of the underlying processes. In this work, recent progress will be discussed with respect to the improved physical modeling of the generation-recombination processes (SRH, Auger, indirect phonon absorption, and free carrier absorption), mobilities, impact of temperature (heating by the lasers), and influence of slow surface state traps (time dependent behavior). In order to quantify the contribution of each parameter in the power curves (representing the probe reflectivity signal versus the pump power), three-dimensional axisymmetric numerical device simulations have been performed. These simulations will be compared to experimental data for a variety of structures (bulk material and chemical vapor deposition grown layers).