Two layer dye photoresist process for sub-half micrometer resolution photolithography

A process for patterning a substrate, comprising the steps of:

• spin coating a first resist layer onto the substrate, the first resist layer comprising a solution of from about 6 to about 9 percent by volume of poly(methylmethacrylate) and a dye having an absorbance of at least about 1.2 at 436 nanometers light wavelength, the dye being present in a ratio of about 1 part dye to 4 parts poly(methylmethacrylate), by volume;
• baking the first resist layer, the amount of material deposited in said step of spin coating a first resist layer being sufficient that the thickness of the first resist layer after baking is from about 0.5 micrometers for about 6 percent poly(methylmethacrylate) to about 1.1 micrometers for about 9 percent poly(methylmethacrylate);
• spin coating a second resist layer overlying the first resist layer, the second resist layer being a positive photoresist material including a naphthoquinone diazide;
• baking the second resist layer, the amount of the material added in said step of spin coating a second resist layer being sufficient that the thickness of the second resist layer after baking is from about 0.4 at about 0.5 micrometers;
• exposing a pattern on the second resist layer with ultraviolet light having a wavelength of greater than about 300 nanometers, and developing the pattern to form an opening through the second resist layer;
• and
• exposing a pattern on the first resist layer with ultraviolet light having a wavelength of less than about 300 nanometers, through the opening in the second resist layer, removing the second resist layer, and developing the pattern to form an opening through the first resist layer, the width of the opening in the first layer being no greater than about 0.5 micrometers.