ELECTROMIGRATION INDUCED STEP BUNCHING ON SI SURFACES - HOW DOES IT DEPEND ON THE TEMPERATURE AND HEATING CURRENT DIRECTION

Recently reported data for an influence of the heating current direction on the micromorphology of Si surfaces have been analyzed on the basis of the hypothesis for electromigration of Si adatoms. The results provide a reasonable explanation of the observed step bunching on the (111) Si surface, which occurs either at moderate or at high temperature depending on the direction (step up or step down) of the heating current. The confrontation with the experimental data results in a negative effective charge of the Si adatoms. The formation of major and minor domains on (001) Si vicinal surfaces under low temperature annealing is also interpreted in accordance with the obtained theoretical results. The force acting on the Si adatoms is estimated to be 0.8 x 10(-16) N and can be created by an electric field of 5 V/cm if the effective charge of an adatom is equal to the elementary electric charge.