Electrical properties of low-dielectric-constant films prepared by PECVD in O 2/CH 4/HMDSO

Abstract

Low-dielectric constant (low-k) films have been prepared by plasma-enhanced chemical vapor deposition (PECVD) from hexamethyldisiloxane (HMDSO) mixed with oxygen or methane. The films are analyzed by ellipsometry, infrared absorption spectroscopy while their electrical properties are deduced from C– V, I– V and R– f measurements performed on Al/insulator/Si structures. For an oxygen and methane fraction equal to 50% and 22%, respectively, the dielectric constant and losses are decreased compared with those of the film prepared in a pure HMDSO plasma. The effect of adding 22% of CH 4 in HMDSO plasma increases the Si–CH 3 bonds containing in the polymer film and as the constant of methyl groups in the film increased the dielectric constant of the film decreases. For this film, the dielectric constant is 2.8, the dielectric losses at 1 kHz are equal to 2×10 −3, the leakage current density measured for an electric field of 1 MV/cm is 3×10 −9 A/cm 2 and the breakdown field is close to 5 MV/cm.