Uniform trench fill recess by means of isotropic etching

摘要

Forming uniformly recessed fills of trench structures which maintain a planar wafer surface without need of any intermediate or final planarisation technique comprises: (i) providing an initial structure comprising at least a sacrificial layer over a substrate, wherein the sacrificial layer may be non-uniform, the structure further comprising a plurality of trenches formed in the sacrificial layer and extending into the substrate and a fill material deposited over the sacrificial layer and filling the trenches, the trenches having a smallest dimension smaller than or equal to twice a desired recess depth; (ii) isotropically etching the fill material to remove it from the sacrificial layer but not below an interface of the sacrificial layer; (iii) removing the sacrificial layer by an isotropical etch selective to the fill material to leave projecting studs of fill material; (iv) isotropically etching the projecting studs of fill material with an etch that is highly selective to the wafer to produce a uniform depth in each of the trenches.