Atomic step distributions on annealed periodic Si(001) gratings

Abstract

One-dimensional (1D) and two-dimensional (2D) periodic square-wave gratings fabricated on Si(001) with repeat spacings of 4 and 5 μm and amplitudes of 0.1-0.25 μm were annealed in ultrahigh vacuum at temperatures between 900 and 1200°C. The surface profiles of the gratings were determined by atomic force microscopy in air after cooling to room temperature. The microscopic structures of the steps and terraces of the gratings were investigated in situ using low-energy electron microscopy. The morphology of the gratings changes with annealing temperature. At 950°C, both ID and 2D gratings have surface profiles resembling truncated sinusoids, with large flat regions at the grating extrema. Between 1050 and 1100°C, the flats at the minima of the 2D gratings expand whereas the flats at the maxima shrink. This asymmetry does not occur for the ID gratings in this temperature range. At 1200°C, the profiles of both the ID and 2D gratings become sinusoidal, with no flats at the extrema. The different morphologies and their temperature dependence can be explained on the basis of the thermodynamics of the surface and the role of surface diffusion and evaporation. © 1997 American Vacuum Society.