MORPHOLOGY AND STRESS INVESTIGATIONS OF SURFACE AND SUBSURFACE REGIONS OF PLASMA HYDROGENATED AND ANNEALED CZOCHRALSKI SILICON

摘要

Hydrogen plasma treatments were applied on Czochralski (Cz) silicon wafers at - 260 - 270 °C in a PECVD-setup. Those plasma treatments cause a structuring of the wafer surface regions down to the sub-100 nm scale. The thickness of the structured layers is in the order of 100 - 200 nm. The impact of the applied plasma, the doping of the substrates, and of the post-hydrogenation annealing on the morphology of the structured surface layers was studied. Annealing was applied up to 1200 °C in vacuum. Investigations were done by scanning electron microscopy (SEM), μ-Raman spectroscopy (μRS), and atomic force microscopy (AFM). The structuring can be explained by a redeposition mechanism. During annealing at T > 800 °C the structured surface layers are dissolved, and Si atoms formerly located in the redeposited crystallites are rebuilt onto the wafer surface. The reconstructed wafer surface and subsurface layers exhibit strong tensile stress up to quite deep wafer regions (~ 10 μm), as was observed by depth resolved u.-Raman analysis.