Adhesion assessment of silicon carbide, carbon, and carbon nitride ultrathin overcoats by nanoscratch techniques

This paper presents experimental results for adhesion assessment of 20 nm ultrathin SiC, amorphous carbon and carbon nitride films deposited on silicon (111) substrates by sputtering. In the experiment, the ultrathin overcoats were scratched by a face-forward Berkovich diamond indenter with a continuous depth sensing nanoscratch system. Experimental results indicate that the nanoscratch system has very good sensitivity for detecting ultrathin overcoat cracking, delamination, and brittle fracture caused by scratching. A well-defined critical load for each film was determined by the nanoscratch techniques. The highest critical load (800 mu N) is found for the CN film and the lowest (500 mu N) is for SiC. Scanning electron microscopy (SEM) investigations to the surface damage of the samples reveal that the SiC overcoat was damaged more severely than other films due to its brittle fracture. The adhesion properties of the three films tested in this work are best in carbon nitride, followed by amorphous carbon and then silicon carbide. (C) 1997 American Institute of Physics.