Modeling the time-dependence of the photoreflectance spectroscopy on ultra-shallow As+ ion implanted silicon

Abstract

Using a high throughput Photoreflectance (PR) spectroscopy setup, a significant temporal behavior of the PR spectroscopy from a wide range of silicon (Si) wafers is observed, induced by optical heating effect. The PR intensity and the built-in electric field enhance on a time scale of several minutes. A diffusion process-based time-dependent model is developed and validated on shallow Arsenic (As+) ion implanted Si layers. A theoretical form of the temporal built-in electric field is determined and used to fit the experimental PR intensity. Modeling the PR temporal effect enables the real time monitoring of As+ diffusion and the measurement of the diffusivity as a function of low implant energy (E: 3 – 7 keV) from which the lattice temperature is derived experimentally. Furthermore, the As+ Shockley-Read-Hall (SRH) carrier lifetime at 300 K is found to be strongly dependent over the same experimental E range. Using the SRH theory, defects formed by As+ implant are studied and related trap density (Ns) are measured versus E assuming unchanged As+ capture cross section.