Planarizing a-C:H and SiO₂ films prepared by bias electron cyclotron resonance plasma deposition

Room-temperature bias electron cyclotron resonance plasma deposition of both carbon- and silicon-based planarization materials has been demonstrated. Planarization layers of amorphous hydrogenated carbon (a-C:H) have been deposited from 1-butene and 1,3-butadiene. Oxide and aluminum features 1-μm deep by 2-μm wide have been planarized to less than 50 nm in height using 1.2-μm-thick a-C:H films. Silicon dioxide layers have been deposited using a mixture of N₂O, Ar, and 5% SiH₄ diluted in N₂. Using films nominally 1.5 μm thick, 800-nm-deep topography can be reduced to less than 50 nm for lines as wide as 3 μm. The planarizing SiO₂ layers have been characterized using ellipsometry and Auger electron spectroscopy and found to have a refractive index and stoichiometry comparable to those of thermally grown gate oxide. The time necessary for planarization and the final film thickness are dependent upon the aspect ratio of the features to be planarized and the deposition conditions.