Characterization of oxygen and nitrogen rapid thermal annealing processes for ultra-low-k SiCOH films

Abstract

Rapid thermal annealing (RTA) processing under N2 and O2 ambient is suggested and characterized in this work for improvement of SiCOH ultra-low-k (k = 2.4) film properties. Low-k film was deposited by plasma-enhanced chemical vapor deposition (PECVD) with decamethylcyclopentasiloxane and cyclohexane precursors. The PECVD films were treated by RTA processing in N2 and O2 environments at 550 °C for 5 min, and k values of 1.85 and 2.15 were achieved in N2 and O2 environments, respectively. Changes in the k value were correlated with the chemical composition of C–Hx and Si–O related groups determined from the Fourier transform infrared (FTIR) analysis. As the treatment temperature was increased from 300 to 550 °C, the signal intensities of both the CHx and Si–CH3 peaks were markedly decreased. The hardness and modulus of the film processed by RTA have been determined as 0.44 and 3.95 GPa, respectively. Hardness and modulus of RTA-treated films were correlated with D-group [O2Si–(CH3)2] and T-group [O3Si–(CH3)] fractions determined from the FTIR Si–CH3 bending peak. The hardness and modulus improvement in this work is attributed to the increase of oxygen content in (O)x–Si–(CH3)y by rearrangement.