Hole printing by packing and unpacking using alternating phase-shifting masks

A method of creating closely spaced contact holes, comprising the steps of:

• (1) providing a substrate, said substrate having been provided with a first layer of material for creation of a pattern of contact holes;
• (2) exposing the surface of said first layer of material with a first mask, said first mask comprising a first and a second pattern of contact holes, said first and said second pattern of contact holes being alternating in phase;
• (3) creating openings in said first layer of material in accordance with said first and second pattern of contact holes;
• (4) depositing a second layer of material over the surface of said first layer of material, including said openings created in said first layer of material in accordance with said first and second pattern of holes;
• (5) exposing the surface of said second layer of material with a mask selected from the group consisting of:
• (i) a second mask comprising a third pattern of holes, said third pattern of holes being aligned with said second pattern of holes, said third pattern of holes being a transparent pattern of holes with a surrounding opaque background surface;
• (ii) a third mask comprising a third pattern of holes, said third pattern of holes being aligned with said second pattern of holes, said third pattern of holes being an opaque pattern of holes with a surrounding transparent background surface;
• (iii) a fourth mask comprising a fourth pattern of holes, said fourth pattern of holes being aligned with said first pattern of holes, said fourth pattern of holes being a transparent pattern of holes with a surrounding opaque background surface;
• (iv) a fifth mask comprising a fourth pattern of holes, said fourth pattern of holes being aligned with said first pattern of holes, said fourth pattern of holes being an opaque pattern of holes with a surrounding transparent background surface;
• and
• (6) creating openings in said second layer of material in accordance with said third or fourth pattern of holes, holes of said third or fourth pattern of holes having a diameter being larger than a diameter of holes of said first and second pattern of holes by a measurable amount.