Novel dual-layer polymeric antireflective coating (PARC) for sub-0.18-μm KrF lithography

Abstract

A novel dual layer polymeric anti-reflective coating (PARC) process has been developed for sub-O.l8jtm KrF lithography. The refractive index, n, and the extinction coefficient, k, of PARC can be tuned to match the optical properties of various substrates. The PARC is a uniform and conformal layer of thin film, which significantly improves the CD uniformity of critical layers such as polysilicon gate and other features over the severe topography. However, the high k PARC has scum issue near the edge of 0.18 m polysilicon line. Some unknown active chemical reaction occurs when high k PARC is directly adhered to the photoresist. The process window is much improved after insertion of a layer of lower k PARC between photoresist and the polysilicori film. With the process simulation, the optimized dual layer of PARC are stacked with 300A of lower k (0.161) and 300A ofhigher k (0.351). However, the process window from the simulation is quite small, the reflectivity ofless than 2% has only for both k values of PARC. The forming rate of the PARC could be controlled to as low as 4.3A per second and with very good film uniformity of less than 5%. We then process the dual layer of PARC on 2500A polysilicon film with 27A gate oxide, a O.8im DOF of process window is obtained for 0. l8tm polysilicon gate line. All the scum near the edge of polysilicon gate line is disappeared with the new dual layer PARC process.