Magnetically enhanced reactive ion etching of submicron silicon trenches

Submicron trench etching of single crystal silicon was studied in a single wafer magnetically enhanced reactive ion etching system. Trenches were etched with both HBr/SiF4/NF3/Iie/02 and HBr/SiF4 etch chemistries. A detailed comparison between the two etch chemistries revealed that acceptable trench profiles could be achieved with either chemistry. The HBr/SiF4/NF3IHeIO2 chemistry was found to be much more selective to the trench hard mask. However it also exhibited a higher density of " black silicon" in large trench areas. Trench profile silicon etch rate and hard mask selectivity were studied as a function of both magnetic field strength and wafer cooling with cooling producing the greater effect. Silicon loading was also found to affect the trench profiles that were obtained with either chemistry. Both of the etch processes exhibited a dependence of silicon etch rate on trench feature size. This dependence was found to become more pronounced as the trench depth increased. Analysis of transmission electron micrograph (TEM) data as well as preliminary electrical results indicate that very little crystal damage occurs with either etch chemistry.