Composition, structure and nanomechanical properties of C–Si–N thin films deposited by ion implantation assisted plasma beam CVD

Abstract

Si- and N-containing a-C:H films were deposited from tetramethylsilane (TMS) vapour and nitrogen onto silicon wafers by an electron cyclotron wave resonance (ECWR) RF plasma beam CVD with simultaneous pulsed N 2 + and Ar + ion bombardment in a plasma immersion ion implantation (PIII) apparatus. Chemical composition and bonding states of the constituent elements were characterised by X-ray photoelectron spectroscopy (XPS) and X-ray induced Auger electron spectroscopy (XAES). Mechanical properties were studied by depth-sensing nanoindentation measurements. Compared to the C / Si = 4 ratio of the precursor, significant loss of C occurred during deposition, resulting in C / Si ranging from 2.39 to 2.90. This effect was most pronounced at low (< 200 V) and high (> 1000 V) self-bias values. Incorporation of nitrogen was significant, resulting in typical N / Si values from 0.7 to 0.9. Formation of extended silicon or silicon carbide clusters could not be detected. The hardness and the reduced modulus of the layers, having maximum values up to 14 and 145 GPa, respectively, decreased with increasing N / Si atomic ratio. C–Si–N layers grown with the application of PIII were characterised by decreased hardness and reduced modulus as compared to those of the layers grown without PIII.