Sub-0.25-μm i-line photoresist: the role of advanced resin technology

Abstract

The use of di-functional monomers such as 2,6- Bis(hydroxymethyl)-p-cresol has allowed the design of novolak resins having alternating architecture with enhanced o,o'-bonding order, specific end-groups and narrow molecular weight distribution. When compared with a conventional m-/p- cresol formaldehyde novolak, the new resins have a lower molecular weight and molecular weight distribution with no p-cresol enriched oligomer fractions. Generally, these resins are used without further processing. With the proper monomer selection novolak resins can be made with the appropriate hydrophilic balance and dissolution characteristics essential for advanced resist development and optimization. By coupling the resin properties with the properties of diazonaphthoquinone sulfonate esters that have a high resolution potential, two advanced sub 0.25 micrometers i- line resist prototypes were developed. With annular illumination, Resist Prototype I demonstrated excellent linear resolution of 0.22 micrometers and an exceptional focus latitude of 1.4 micrometers and 1.7 micrometers for the 0.23 micrometers and 0.25 micrometers dense L/S, respectively; while Resist Prototype II showed linear resolution of 0.18 micrometers L/S and outstanding focus latitudes of 1.6 micrometers and 1.7 micrometers for the 0.21 micrometers L/S and the 0.23 micrometers L/S, respectively.