Nanohardness and contact angle of Si wafers implanted with N and C and Al alloy with N by plasma ion implantation

Surfaces of silicon wafers implanted with N and C, respectively, and aluminum 5052 implanted with N alone by plasma immersion ion implantation (PIII) were probed by a nanoindentor and analyzed by the contact-angle method to provide information on surface nanohardness and wettability. Silicon nitride and silicon carbide are important ceramic materials for microelectronics, especially for high-temperature applications. These compounds can be synthesized by high-dose ion implantation. The nanohardness of a silicon sample implanted with 12-keV nitrogen PIII (with 3×1017 cm−2 dose) increased by 10% compared to the unimplanted sample, in layers deeper than the regions where the formation of the Si3N4 compound occurred. A factor of 2.5 increase in hardness was obtained for C-implanted Si wafer at 35 keV (with 6×1017 cm−2 dose), again deeper than the SiC-rich layer. Both compounds are in the amorphous state and their hardness is much lower than that of the crystalline compounds, which require an annealing process after ion implantation. In the same targets, the contact angle increased by 65% and 35% for N- and C-implanted samples, respectively. Compared to the Si target, the nitrogen PIII-irradiated Al 5052 (with 15 keV) showed negligible change in its hydrophobic character after ion implantation. Its near-surface nanohardness measurement showed a slight increase for doses of 1×1017 cm−2. We have been searching for an AlN layer of the order of 1000 Å thick, using such a low-energy PIII process, but oxide formation during processing has precluded its synthesis.