Ultra-large scale integrated circuits (ULSIs) have been continually scaled down according to Moore’s law. This canimprove their power consumption and operation frequency but not the RC delay of their interconnections; to this end,super low dielectric constant films are required. We propose a novel method to fabricate porous SiO_2 films with a superlow dielectric constant by F_2 laser deposition. In this method, a quartz target is evaporated by F_2 laser ablation invacuum-chamber-controlled Ar partial pressure. The evaporated SiO_2 molecules are agglomerated in the vacuum, andthe size of the SiO_2 nanoparticles are controlled by the Ar partial pressure. Porous SiO_2 films are formed on a Sireceivingsubstrate, which is placed in front of the quartz target.The pulse duration of the F_2 laser was approximately 20 ns, and the repetition rate of laser shots was 100 Hz. The basepressure of the vacuum chamber was 5 × 10~(?3) Pa. Then, Ar gas was introduced into the vacuum chamber through a massflow controller to control the Ar partial pressure.The dominant size of the SiO_2 nanoparticles decreased from 1.5–2.0 nm to 1.0–1.5 nm with the Ar partial pressuredecreasing from 20 Pa to 4.5 Pa. In addition, the relative dielectric constant k of the porous SiO_2 film formed at an Arpartial pressure of 4.5 Pa was 2.8, which is lower than that of thermal SiO_2 (k = 4.0). In addition, the leakage current ofthe nanoporous SiO_2 film was almost equal to that of the thermal SiO_2 film. From these results, we conclude thatnanoporous SiO_2 films with a super low dielectric constant can be formed by F_2 laser deposition.
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