Paul Richard West

Contrast Enhancement - A Route To Submicron Optical Lithography

A new method for the production of submicron photopatterns is described. Good quality images are obtainable even under very low contrast illumination through the use of photobleachable materials in conjunction with standard photoresists. The method consists of applying a thin photobleachable layer to the photoresist surface prior to the conventional exposure step. The bleachable layer (contrast-enhancing layer or CEL) is subsequently removed and the resist developed in the ordinary way. Examples of vertical-walled submicron patterns fabricated using an Optimetrix 10:1 DSW system demonstrate that the CEL process compares well with other advanced photolithographic techniques.

Contrast Enhancement Materials For Mid-Uv Applications

The use of nitrones as contrast enhancement materials has been extended to the mid-UV region. Diarylnitrones, which function effectively as near-UV contrast enhancement materials, have been found to be less suitable for mid-UV printing because of secondary photochemical reactions. α-Aryl-N-alkylnitrones, however, can be designed to absorb efficiently and photobleach cleanly over a wavelength range of about 280 to 350 nm. Arylalkylnitrones are much more resistant to hydrolysis than are their diaryl counterparts and have been successfully formulated as aqueous solutions. Submicron resist patterns have been printed with a scanning projection aligner operating in the mid-UV through the use of a contrast enhancement material based upon an arylalkylnitrone.