Non-plasma-based technologies to augment backend processing in future ULSI

The solution to the problem of increased resistance-capacitance (RC) delay in the present day ULSI is to use porous low-k dielectric films (k = 2.0) along with Copper interconnects. There are a number of issues with Cu/low-k integration, such as Cu diffusion in the porous low-k film, moisture penetration, and damage during backend processing steps like etching and photoresist ashing. Water vapor is introduced into the low-k layer during ashing of the photo resist, which raises the k value to typically above 3. We have successfully addressed all these issues in the case of hydrogen silsesquioxane (HSQ) (k = 2.8) with the help of a non-plasma-based hot-wire-induced chemical-vapor process (HWCVP). With the help of this process, we have also been successful in developing an ultra-thin hydrogenated amorphous silicon-carbon-based barrier layer that completely avoids copper diffusion and shows a higher resistance to electromigration.