Antireflective bi-layer hardmask including a densified amorphous carbon layer

Abstract

An amorphous carbon layer of an antireflective bi-layer hardmask is processed to increase its density prior to patterning of an underlying polysilicon layer using the bi-layer hardmask. The increased density of the layer increases its resistance to polysilicon etch chemistry, thus reducing the likelihood of patterning inaccuracies resulting from amorphous carbon depletion during polysilicon etch, and enabling the patterning of thicker polysilicon layers than can be reliably patterned without densification. The increased density also reduces stresses, thus reducing the likelihood of delamination. Densification may be performed by UV or e-beam irradiation after formation of an overlying protective layer. Densification may also be performed by annealing the amorphous carbon layer in situ prior to formation of the overlying protective layer. In the latter case, annealing reduces the amount of outgassing that occurs during formation of the protective layer, thus reducing the formation of pin holes.