PHASE SELECTIVE DEPOSITION OF BORON ACHIEVED BY CRYSTALLIZATION CONTROL

The growth kinetics and phase composition of boron films deposited by chemical vapor deposition from H2/BCl3 mixtures depend strongly upon the choice of substrate material. We have demonstrated phase-selective deposition of amorphous boron (a-B) and crystalline alpha-rhombohedral boron (alpha-B) on a substrate patterned with Ti and Mo regions. a-B was obtained on Ti at growth temperatures up to 1500 K, well above the normal stability temperature of the amorphous phase, while at the same time alpha-B was obtained on the exposed Mo region of the substrate. The interface between the two phases remained abrupt and vertical for film growth to thickness > 10-mu-m.