The Spectroscopy of Crystal Growth Surface Intermediates on Silicon

Abstract

The direct spectroscopic analysis of the monolayer of intermediate species present during crystal growth by CYD methods remains a very desirable goal which has yet to be achieved. While the application of i.r. spectroscopy to analysis of sub-monolayers on metal single crystal surfaces is widespread, using the reflection-absorption technique^1,2 (RAIRS), a similar approach to semiconductor surfaces is less sensitive and open to a number of variations. The most successful of these is the attenuated total reflectance (ATR) method in which the i.r. beam is channelled inside the crystal, which has bevelled edges in the form of an ATR prism, Fig. 1. Good quality spectra of surface SiH_n species have been recorded using ~50 reflections³. The ATR technique cannot be applied to crystals which absorb i.r. radiation, even weakly, because of the considerable internal path length (~10 cm for 50 reflections). For this reason the multi-phonon absorption bands of silicon limit its use to the region above ~1000 cm⁻¹ so that the silicon-hydrogen deformation modes are inaccessible. It may also be difficult to use the ATR method routinely under growth conditions because of the constraints on sample dimensions and difficulty of alignment.