Synthesis of Silicon Carbonitride for the Machining of Resonant Nanomechanical Biosensors

Abstract

We report a study on the plasma-enhanced chemical vapor deposition of silicon carbonitride, as well as the resonant behavior of nanomachined SiCN structures. Films with thicknesses of 1 um, and 200 nm were deposited at varying gas ratios using ammonia (NH3), nitrogen (N2), and diethylsilane (DES) as precursors. X-ray photoelectron spectroscopy revealed high nitrogen and low carbon content in films deposited at high NH3:DES gas flow ratios. Selected samples annealed at varying temperatures experienced shifts in stress towards tensile of Δσ = 235 MPa, 432 MPa, 724 MPa, and 1140 MPa, at annealing temperatures of T = 400 °C, 500 °C, 600 °C, and 700 °C respectively. Infrared spectroscopy reported a loss of incorporated hydrogen as a mechanism of stress modulation. Resonant assaying of cantilevers fabricated from 200 nm-thick SiCN yielded root-modulus-over-density values of √(E/ρ) = 6.95 × 103 m/s and √(E/ρ) = 8.35 × 103 m/s, comparable to those of silicon.