Silicon nitride islands as oxidation masks for the formation of silicon nanopillars

We have used silicon nitride islands as oxidation masks for the formation o f nanometer-scale silicon pillars. For the growth of silicon nitride island s on the Si(1 1 1)-7 X 7 surface, two different methods were used: (1) 100 eV N-2(+) ion exposure at room temperature followed by subsequent post anne aling at 980 degrees C and (2) N-2 exposure at 800 degrees C. Scanning tunn eling microscope images for the two differently prepared surfaces showed a submonolayer coverage of nanometer-size silicon nitride islands. On these s urfaces, oxygen was exposed at high temperatures where silicon etching was dominant over oxide formation. It was found that those silicon nitride isla nds successfully worked as oxidation masks to form silicon nanopillars as h igh as several nanometers via a selective oxygen etching of silicon. Silico n nanopillars of uniform sizes but with nonuniform heights were obtained in the case of N-2(+) ions, while those with a distribution of nonuniform siz es but homogeneous heights were formed in the case of N-2 gas. Such differe nt results are explained in terms of differences in the nitridation reactio n between the two preparation methods. (C) 1999 American Vacuum Society. [S 0734-2101(99)11204-1].