Hard plasma chemical coatings based on silicon carbon nitride

Silicon carbon nitride (SiCN) coatings deposited on a silicon substrate are produced by plasma-enhanced chemical vapor deposition (PECVD) using methyltrichlorosilane (MTCS), nitrogen, and hydrogen as starting materials. The coatings are characterized with AFM, XRD, and FTIR. Their mechanical properties are determined with nanoindentation. The abrasion wear resistance is examined using a ball-on-plane (calowear) test and adhesion to the base using a scratch test. The x-ray diffraction indicates that the coatings produced at moderate F_N are nanostructured and represent β-C₃N₄ crystallites embedded into the amorphous a-SiCN matrix. The coatings deposited at a higher nitrogen flow rate are amorphous. The nanostructure is supposed to result from an increase in hardness (25 GPa) and Young’s modulus (above 200 GPa). The tribological tests have revealed that the friction coefficients of the coatings containing nitrogen are two to three times smaller than those based on SiC and deposited on a silicon substrate. The ball-on-plane tests show that the nanostructured coatings also exhibit the highest abrasive wear resistance. These findings demonstrate that the SiCN films deposited using MTCS show good mechanical and tribological properties and can be used as wear-resistant coatings.