High definition molecular array feature generation using photoresist

A method for providing an array, comprising:

• a) irradiating a substrate comprising a plurality of masked spot regions and an unmasked boundary region between the plurality of masked spot regions, whereby a photoresist in the boundary region is degraded to render the boundary region available for blocking or ablation of oligonucleotide molecules in the boundary region, whereas the spot regions are protected by a photoresist in the spot regions from oligonucleotide blocking or ablation;
• b) blocking or ablating oligonucleotide molecules in the boundary region;
• c) irradiating the substrate to render an oligonucleotide molecule immobilized in a first one or more of the spot regions on the substrate available for oligonucleotide attachment, whereas an oligonucleotide molecule immobilized in one or more other spot regions on the substrate are not available for oligonucleotide attachment;
• and
• d) attaching a first oligonucleotide of at least four nucleotides in length to the oligonucleotide molecule immobilized in the first one or more of the spot regions to provide an extended oligonucleotide molecule in the first one or more of the spot regions.