Patent ID: 7172969

Claim:
A method of preparing a feature on a substrate comprising: forming a film stack on a substrate, said film stack comprising a polysilicon layer, a first mask layer formed on said polysilicon layer, a second mask layer formed on said first mask layer, a third mask layer formed on said second mask layer, a fourth mask layer formed on said third mask layer, and a layer of light-sensitive material formed on said fourth mask layer; forming a pattern having a first critical dimension in said layer of light sensitive material using lithography; trimming said pattern to form a second critical dimension in said pattern less than said first critical dimension; transferring said pattern to said fourth mask layer; transferring said pattern to said third mask layer; transferring said pattern to said second mask layer; transferring said pattern to said first mask layer; and transferring said pattern to said polysilicon layer, wherein a final critical dimension of approximately 25 nm or less is achieved, wherein said pattern is transferred to said polysilicon layer via a main etch step preceded by a breakthrough process step, and wherein said breakthrough process step facilitates removal of oxidized silicon.