Lithographic image size reduction

Process for forming a mask on a substrate surface for integrated circuit manufacture comprising:

• providing a substrate covered with a relatively thick layer of a first material;
• coating said first material with a photosensitive layer having an opening of a minimum size dictated by the resolution limit of lithography, said opening having substantially vertical surfaces;
• depositing a conformal layer of an insulator material on said first material including said vertical surfaces and on the substrate exposed by said opening;
• anisotropically etching to remove said conformal layer from everywhere except said walls of said opening, thereby reducing the size of said opening by approximately twice the thickness of said conformal layer;
• and
• anisotropically etching said first material layer to transfer thereto an image of said opening of reduced size in said photosensitive layer and transform said first material layer into a mask for said substrate.