A new positive DUV photoresist optimized for 0.25 μm isolated lines

This paper reports on the Shipley/IBM developed UV4 positive DUV photoresist, which is particularly suitable for gate array applications. This resist shows ≥1.4 μm DOF for 0.25 isolated lines and ∼20% exposure latitude. The UV4 photoresist has been designed to have relatively high developer selectivity (∼8) and an Rmax of 3100Å/s. In this case, we have opted for a lower developer selectivity and Rmax than those of UVIIHS photoresist. The UV4 photoresist also shows good photospeed, ≤30 mJ/cm2, excellent postexposure delay stability, ≥1 hour at 0.25 μm, and better etch resistance than UVIIHS resist.