Novel thermoplastic SOC materials for planarization use in multilayer lithography process

As advancement of semiconductor to 1Xnm nodes and beyond, the importance of multilayer lithography process is increasing. Generally, multilayer consists of photoresist layer, middle layer and underlayer. Theses layer materials prefer spin-on type to CVD type from the viewpoint of the cost of ownership and process simplicity. The key requirements which spin-on materials must satisfy are to be soluble in organic solvent and insoluble after bake process to coat upper layer materials, gap filling and planarization performances, etch controllability and easy strippability. In particular, the solubility switchable property, the gap filling and planarization performance on topo-patterned substrate are receiving much attention recently. In this report, novel spin-on carbon (SOC) material for multilayer lithography process will be described. The SOC materials we present here consist of the thermoplastic polymer which we originally developed and PGMEA or cyclohexanone as solvent, there is no any other additive. This varnish can be applied to a substrate by spin-on coating. It is worth noting that the SOC layer after bake process becomes insolubilized for PGMEA. This property enables to use PGMEA when stacking upper layer. Because of the intrinsic thermal flow nature of our thermoplastic polymer, the gap filling and planarization performances are excellent for the topo-patterned substrate which includes pad, open and dense line area. The etch rate of the SOC layer for C_xF_y gas is constant, so these materials have good etch controllability. Therefore, these SOC materials could be potentially candidate for planarization use in multilayer lithography process.