A greyscale lithography scheme using direct write lithography can create dual damascene polymer RDLs. This approach eliminates the need for a second lithography pass, reducing cost and eliminating overlay between trench and via layers compared to a semi-additive process (SAP). This reduction in overlay allows for reduced capture pad diameters and ultimately improved IO density. However, the industry does prefer several approaches to the same challenge. Hence, another alternative is the lithography-etch, lithography-etch (LELE) patterning process that involves sequential trench lithography & etch and then, via lithography & etch, decoupling the polymer from its photo-imageable requirements. Although this approach is more complex and increases overlay risk, it allows for optimized control of sidewall profile, CDs, and trench depth, leading to tight resistance distributions. Regarding cost, each RDL layer with the LELE approach requires extra lithography, CVD, and two reactive ion etch (RIE) steps. Depending on specific requirements, the two methods can be considered for advanced fan-out applications. This paper presents a physical and electrical analysis of ultra-fine pitch dual damascene RDLs in serpentine-comb and 4-point Kelvin resistance structures fabricated on 300 mm wafers using greyscale lithography and LELE patterning. This work, for the first time to our knowledge, demonstrates fine-pitch dual damascene RDLs using direct write greyscale lithography. Additionally, the reliability of the dual damascene polymer RDL will be discussed.