Topside anti-reflective coating process and productivity improvements on KrF lithography

Topside anti-reflective coatings (TARC) are used in microelectronics fabrication to control standing wave formation during the patterning process. By changing the phase of the light that is reflected from the substrate, interference effects of thin photoresist films are minimized. Filtering and dispensing these fluids have proven to be difficult, as they are prone to micro-bubble formation due to surfactant additives. Surfactants will encapsulate micro-bubbles that form during filtration and dispense. The acidity of TARC is also of concern with regards to resist dark loss, especially at point of dispense. Minimization of TARC process defects is of paramount significance in a manufacturing environment. Reduced defect levels can increase overall yield and tool availability. In this study, we examined reducing the volume of trapped air and the resist dark loss associated with TARC acidity to prevent the formation of defects. Due to the inherent material properties of TARC, the handling, chemical priming, preventative maintenance, pump type, filter type and size, vent interval, filtration rate, idle/periodic dispense frequency methodology, and on-wafer dispense methodology must be considered to prevent in-film and surface defects associated with micro-bubbles and the TARC acidity. Defect reduction and increased tool availability was accomplished by examining and optimizing tool hardware and functionality, examining and optimizing filter media and size, examining and optimizing pump purge/vent sequences and frequency, improving overall pump knowledge, improving filter change procedure and maintenance, and understanding and reducing dark loss issues associated with acidity of TARC chemical.