Evolution of Surface Morphology With Hydrogen Dilution During Silicon Epitaxy by Mesoplasma CVD

The influence of hydrogen in high-rate and low-temperature silicon epitaxy under mesoplasma conditions has been investigated from growth precursors and film structural evolution points of view. In situ small-angle X-ray scattering measurement has confirmed that silicon nanoclusters that are around 2 nm in size and having a loosely bound structure were formed as growth precursors, independent of the amount of hydrogen. Surface morphological analysis, on the other hand, has revealed that the deposition mechanism changes from surface diffusion to primarily step flow with hydrogen addition due potentially to the anisotropic etching of the silicon surface. Atomically smooth epitaxial films with Hall mobilities of up to 300 cm²/(V middots) were deposited accordingly at high partial pressures of hydrogen (> 220 mtorr), while polycrystalline films were produced at lower hydrogen amounts and still retaining relatively high electric properties.