Optimization of Point-Of-Use Filtration for Metal Oxide Photoresist

Abstract

While great advances have been made to move extreme ultraviolet (EUV) lithography toward manufacturing readiness, a difficult challenge remains. Although standard chemically amplified resists (CAR) can be exposed with EUV, these materials struggle to achieve resolution targets and are not nearly as sensitive as those created for ArF exposure. Non-CAR resists, such as metal-oxide resists, offer an alternative that achieve both EUV resolution and sensitivity targets. However, the inclusion of metal oxides poses a challenge to traditional filtration designed to remove unwanted dissolved contaminants from the fluid stream. Ultrahigh molecular weight polyethylene (UPE) filters have been used for metal oxide EUV resist filtration because of high retention efficiency and excellent photochemical compatibility.

This paper describes our joint effort to improve Inpria metal oxide EUV resist defectivity using filtration optimization. A study comparing various Point-of-Use (POU) filters was conducted to identify filtration solutions that reduce defects in Inpria metal-oxide EUV resist coatings. Several filters utilizing a variety of retention ratings and membrane designs were installed on a TEL Clean Track (TM) Act (TM) 12. A metal oxide EUV resist was filtered and coated on wafers that were subsequently analyzed for total wet particle counts. This study presents the efficacy of optimized filtration design to reduce defects in metal oxide EUV resists and provides a recommendation to achieve low wafer coating defects.