Photosensitive polybenzoxazole precursor compositions

A photosensitive resin comprising:

• a polybenzoxazole precursor bearing acid labile functional groups having the structure:
• ##STR13## wherein k.sub.1 is an integer of 1 or 2, k.sub.2 is an interger of 0 or 1, and the sum of k.sub.1 and k.sub.2 is 2;
• Ar.sub.1 is a tetravalent aromatic, aliphatic, or heterocyclic group, or mixtures thereof;
• Ar.sub.2 is a divalent aromatic, aliphatic, or heterocyclic group or siloxane group;
• D is a monovalent acid labile group selected from the group consisting of acetals, ketals, carbonates, ethers, silyl ethers, moieties containing t-butyl ester groups and mixtures thereof;
• n is an integer from 20 to 200, where a portion of Ar.sub.1 can be a divalent aromatic, aliphatic, or heterocyclic diamine moiety such that the fraction of diamine compound is 0-60 mole % and the sum of diamine and diamino dihydroxy compound is 100%.

A process for preparing an polybenzoxazole precursor bearing acid labile functional groups having a blocking level about 1% to 100%, comprising one of the following steps of:

• (a) reacting a polybenzoxazole precursor with a vinyl ether in the presence of an acid catalyst;
• (b) reacting a polybenzoxazole precursor with a di-t-butyl dicarbonate in the presence of a base;
• or
• (c) reacting a polybenzoxazole precursor, an alcohol, and a t-butyl vinyl ether in the presence of an acid.

A process for the preparation of a heat-resistant relief image comprising the steps of:

• a) coating on a substrate, a heat resistant positive-working photosensitive composition comprising an polybenzoxazole precursor bearing acid labile functional groups, a photoacid generator, and a solvent, thereby forming a coated substrate;
• b) exposing said coated substrate to actinic radiation;
• c) post exposure baking said coated substrate at an elevated temperature;
• d) developing said coated substrate with an aqueous developer, thereby forming a developed substrate;
• and
• e) baking said developed substrate at an elevated temperature to convert the polybenzoxazole precursor to a polybenzoxazole.