Effect of thermal treatment on carbon-doped silicon oxide low dielectric constant materials

Carbon-doped silicon oxide (SiOCH) low dielectric constant (low-k) material is a good candidate for advanced interconnect technology. Good thermal stability of the dielectric is required due to the many thermal processes involved during IC fabrication. The thermal stability of tetramethylcyclotetrasiloxane (TMCTS) based plasma-enhanced chemical vapor deposition (PECVD) carbon doped low-k material with annealing temperature from 400 to 800 degrees C in N2 was studied. The thermal stability temperature of TMCTS based carbon doped low-k material is 600 degrees C. Above 600 degrees C annealing, the thermal energy can break Si-CH3, Si-C, Si-H, and C-H bonds leading to outgasing, which results in film composition change, weight loss, and thickness shrinkage. Film composition changes, especially carbon loss and oxygen incorporation, can degrade its reliability extremely. Carbon is desorbed in the form of CH4, CO, and other hydrocarbon.