MECHANISM OF SURFACE-ROUGHNESS IN HYDROGEN PLASMA-CLEANED (100)SILICON AT LOW-TEMPERATURES

Surface roughening and defect formation of (100) Si at low temperature s during electron cyclotron resonance hydrogen plasma cleaning are stu died in an ultrahigh vacuum environment, and a new model is proposed t o explain their mechanisms. The effect of process parameters on surfac e roughness is quantitatively analyzed by atomic force microscopy and reflection high energy electron diffraction. Crystalline defect morpho logy is studied by transmission electron microscopy to understand its role in surface roughness. Surface roughness is strongly related to {1 11} platelet defects at the Si subsurface region and subsequent prefer ential etching at positions where {111} platelet defects intersect the Si surface. The formation of {111} platelet defects is determined by the subsurface hydrogen concentration, which is determined by incident hydrogen flux and substrate temperature. The preferential nucleation of etching reactions on the {111} platelet may be explained by the cla ssical nucleation theory. Hydrogen ion flux and substrate temperature can be controlled successfully to tailor {111} platelet defect formati on and hence, surface roughness.