Method of forming sub-half micron patterns with optical lithography using bilayer resist compositions comprising a photosensitive polysilsesquioxane

A method for producing a photoresist relief image having at least two layers and having sub-half micron features comprising the steps of:

• (a) applying, to a substrate, a polymer underlayer having a refractive index in the range of about 1.58 to 1.7 at the wavelength of the exposing ultra violet radiation;
• and
• (b) overcoating said polymer underlayer with a composition comprising a photosensitive hydroxyaromatic silsesquioxane polymer partially esterified with diazonaphthoquinone groups having the formula ##STR5## wherein (1) R.sub.1 to R.sub.4 are each individually H or Si(CH.sub.3).sub.3 ;
• and
• (2) each individual Ar.sub.1 to Ar.sub.8 group is selected from the group consisting of p-hydroxyphenyl, p-methoxyphenyl and p-(2-diazo-1-naphthoquinonesulfonyloxy)phenyl, as represented respectively by the formulas ##STR6## so that the molar ratio in said polymer of p-hydroxyphenyl groups to p-methoxyphenyl groups to p(2-diazo-1-naphthoquinonesulfonyloxy)phenyl groups is in the range from 67:25:8 to 58:30:12,
• (3) DQ is a 2-diazo-1-naphthoquinone-4 residue, a 2-diazo-1-naphthoquinone-5 residue as represented respectively by the formulas ##STR7## or mixtures thereof;
• and (4) n is an integer from 5 to 9;
• and
• (5) o and p are, independently, 0 or 1;
• and
• (c) imagewise exposing the photosensitive silsesquioxane polymer to ultraviolet radiation to form a latent image;
• and
• (d) developing the latent image to form a relief image in the silsesquioxane polymer;
• and
• (e) transferring the relief image to the polymer underlayer with 0.sub.2 RIE.