The lithographic performance of an environmentally stable chemically amplified photoresist (ESCAP)

Improved stabilization of chemically amplified photoresist images can be achieved through reduction of free volume by film densification. When the host polymer has good thermal stability, the softbake temperature can be above or near the glass transition temperature (T-g) of the polymer. Annealing (film densification) can significantly improve the environmental stability of the photoresist system. Improvements in the photoacid generator, processing conditions, and overall formulation coupled with high NA (numerical aperture) exposure systems afford 200 nm linear resolution with excellent post-exposure delay stability. In this paper, lithographic data will be shown for the improved ESCAP photoresist system (now called UVIIHS) currently under development for DRAM and logic device technology. We will review the photoresist system, along with process- and formulation- related experiments on device levels and substrates demonstrating excellent 250nm and sub-250nm process windows.