Morphology evolution of epitaxial SiGe and Si in patterns

Abstract

The morphology of Si and Si0.73Ge0.27 (SiGe), deposited in 〈100〉 and 〈110〉 oriented patterns on (001) Si wafers, has been studied after an annealing step. Thin films of 19nm have been realized by selective epitaxy in patterns of varying size and have subsequently been annealed in the epitaxy chamber. It has been shown that the morphology depends on both the size and orientation of the patterns. At the edges and corners of the patterns, thermal rounding of the faceted as-deposited morphology occurs during annealing, leading to a certain local thickening of the film. The influence of this effect on the morphology has been found to increase with decreasing pattern size. Due to the additional contribution of strain relaxation the effect is enhanced by a factor of 2 in the case of SiGe. In large patterns, anisotropic SK-like strain relaxation of SiGe along 〈100〉 directions results in smooth 〈100〉 oriented edges and undulated 〈110〉 oriented edges. In small patterns, the morphology results in ridges when the pattern orientation is parallel to the direction of strain relaxation and in faceted islands when the pattern orientation is turned by 45°. In the case of very narrow lines, the anisotropic loading effect during deposition controls the morphology after annealing. The result is the formation of instabilities in 〈100〉 oriented lines, for both Si and SiGe.