The use of multilayer processes in advanced ArF patterning schemes continues to increase as device critical dimensions shrink. In a multilayer stack, underlayer materials play a critical role in terms of gap fill, planarization and etch resistance to enable high resolution and high aspect ratio patterning. The emerging quadlayer imaging process requires a unique spin on carbon (SOC) layer with high thermal stability to withstand subsequent deposition of an inorganic hard mask layer, commonly deposited via chemical vapor deposition (CVD). The thermal stability requirement associated with CVD compatibility largely limits the options of organic materials, which mostly decompose in the 300-450°C range. Thermal shrinkage and coefficient of thermal expansion (CTE) differences between layers are other key considerations in designing a high temperature stable, CVD compatible SOC material. Furthermore, the SOC polymer resin must be compatible with solvents and spin on products commonly used in the FAB. This paper highlights the development of a novel CVD compatible HT-SOC platform with excellent thermal stability (>500°C) and good FAB drain line compatibility. In addition, this polyaromatic SOC platform shows various improvements compared to traditional Novolacbased SOC, including reduced shrinkage, good gap fill, improved planarization, and low defectivity. Robust formulation design, high quality raw materials, and advanced metal removal technique synergistically enabled manufacturing of multigallon HT-SOC product with high quality. Application specific versions are available for more demanding planarization requirement and applications that require good adhesion to metal substrate. In addition, a newly developed method for quantitative measurement of long-range planarization was used to validate new material designs aimed at improving planarization.