Ultra- Thin Conformal Pore-Sealing of Low-k Materials by Plasma-Assisted ALD

Abstract

We have developed a plasma activated atomic layer deposition (PA-ALD) process to produce a few-nm-thick conformal SiO2 cap layer that seals the pores of patterned and unpatterned self-assembled mesoporous low-k dielectric films for integrated circuit fabrication. Tetraethoxysilicate plus O2 and hexamethyldisilazane plus O2 were used as the ALD precursors. In both cases, the plasma was formed in Ar and O2 during the O2 exposure step. By choosing the plasma conditions appropriately, we were able to ensure that unlike conventional ALD, the SiO2 deposition did not occur in the pores. We found that the PA-ALD process did not change the dielectric constant of the mesoporous film. Additionally, we found that for a 1.6 nm thick film, the N2 permeance of the capped film was reduced by a factor of 1600 compared to the uncapped film.