Method of high density plasma CVD gap-filling

A plasma process for providing SiO.sub.x filled gaps between electrically conductive lines on a semiconductor substrate comprising steps of:

• providing a substrate in a process chamber of a plasma reactor;
• simultaneously introducing a silicon-containing reactant, a noble gas selected from the group consisting of xenon, krypton or mixture thereof, and an oxygen-containing reactant into the process chamber;
• growing a SiO.sub.x film on the substrate by plasma phase reacting the silicon containing reactant on a surface of the substrate, the SiO.sub.x film being deposited in gaps between electrically conductive lines on the substrate wherein the gaps have widths below 0.5 .mu.m and aspect ratios of gap height to gap width of at least 1.5:1, the silicon containing reactant comprising SiH.sub.4 and the oxygen containing reactant comprising O.sub.2, the O.sub.2 being supplied in a ratio of O.sub.2 /SiH.sub.4 of .ltoreq.1.05 and the deposited film having a substantially uniform refractive index in the range of 1.47 to 1.49;
• and
• sputtering film deposits on sidewalls of the gaps during the film growing step by applying an RF bias to the substrate, the sputtering facetting corners of the gaps and preventing void formation in the SiO.sub.x filled gaps.