Experimental evidence of photoeffects in silicon rapid isothermal diffusion

Abstract

Rapid isothermal processing (RIP) based on incoherent radiation as a source of optical and thermal energy is emerging as a key low thermal budget technique for the processing of semiconductor devices and circuits. The continuing development of RIP technique for the fabrication of electronic and optical devices requires a microscopic understanding of various phenomena associated with RIP. Junction formation by diffusion process is an integral part of all semiconductor devices. In this letter, we have shown that for identical thermal budget, different values of sheet resistivity are observed when the samples are irradiated from front or back. These results cannot be explained by the various process models and computer aided design tools available in the literature. We have offered a qualitative explanation of the observed results based on the role of photoeffects in RIP. The availability of high-energy photons in the front irradiation configuration and consequent electronic excitation can lead to higher diffusion coefficients as well as higher activation of dopants, compared to the back irradiated case.