Superconformal coating and filling of deep trenches by chemical vapor deposition with forward-directed fluxes

The authors report a superconformal chemical vapor deposition method that affords bottom-up filling of trenches with oxide: the film growth rate increases with depth such that the profile of material develops a “V” shape that fills in along the centerline without a seam of low density material. The method utilizes low pressures of a metal precursor plus a forward-directed flux of co-reactant (water) at a lower pressure than the precursor. Under these conditions, many of the co-reactant molecules travel ballistically to the trench bottom where a fraction of them reflect. This scattering, which creates a virtual source of co-reactant from the trench bottom, leads to a superconformal growth process whose rate is highest at the bottom and declines toward the opening. Simultaneous with this superconformal component is the typical subconformal growth process due to the portion of the co-reactant flux that enters the trench opening isotropically; with a sufficiently large forward-directed flux, however, the over...