Analysis of surface defects in Si

Author： Colston Gerard Myronov Maksym Rhead Stephen Leadley David

E-ISSN： 1361-6641|30|11|114003-114008

ISSN： 0268-1242

Source： Semiconductor Science and Technology, Vol.30, Iss.11, 2015-11, pp. : 114003-114008

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Abstract

Strained Si_1−yC_y epilayers have been grown on Si (001) by reduced pressure chemical vapor deposition, using low-cost precursors disilane and trimethylsilane. Substitutional C incorporation has been achieved in strained epilayers up to y = 1.5%, while higher C content of at least 2.4% is observed in relaxed layers. These results are comparable to the highest concentrations achieved using more highly reactive, but expensive, precursors. These relatively high C content epilayers were found to form defects throughout growth attributed to the clustering of C adatoms, which result in localized accelerated amorphous growth and, consequently, hillocks forming on the epilayer surface. The formation, size and distribution of these surface defects has been analyzed through the use of various microscopic techniques. The size and density of these structural defects increases with both C content and epilayer thickness. In our layers of fixed growth time, substitutional C compositions above 1.5% causes hillocks to fuse on the surface; subsequently amorphous growth occurs, which forms an amorphous layer over the crystalline Si_1−yC_y epilayer and hence prevents further epitaxy or reliable device fabrication. The results of this investigation suggest that substitutional C composition of below 1.5% could be achieved without the need for expensive and volatile precursors or complex growth processes, assuming sufficiently thin layers are grown.