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A new efficient inorganic anti-reflective coating (ARC) layer which refers to silicon oxynitride (SiOxNy) is evaluated and applied to 0.35 micrometers and 0.3 micrometers technologies using i-line lithography. This new bottom ARC layer can be applied to various substrates such as poly silicon, Wsix and Al by controlling the deposition conditions to change n&k values and film thickness, not only for i-line lithography but also for DUV lithography. Hereby we present the study of this new inorganic bottom ARC layer on poly silicon for i-line technology. The results show that it can enhance the process window by 30% for 0.35 micrometers 0.3 micrometers devices. The resolution limit of i-line lithography can be pushing down to 0.25 micrometers by reducing thin film interference in photoresist. Swing curve effect is reduced by more than 5X as compared to standard resist process. CD uniformity for 0.35 micrometers device is improved significantly across 8 inch wafers using bottom ARC. Notching and necking effects are totally eliminated as compared to standard top ARC process with 18% notching and necking effects. Optical proximity effects are reduced by 30%. No impact on overlay is found using SiON bottom ARC. Etching this SiON ARC layer is investigated and it is found that reasonable good etch profile can be achieved. Thin film uniformity variation study shows that +/- 50 A film thickness variation can be tolerated with +/- 5% CD variation. Thermal stability study of the ARC layer shows no peeling or bubble found at high temperature of 850 degree(s)C. No removal of this ARC layer is needed. In addition, the further study also shows that straight resist profile can be obtained by fine tuning the ARC layer thickness. As compared to organic bottom ARC, SiOxNy bottom ARC has the advantages of low cost of ownership, less defect density and shorter cycle time is needed. Prolith/2 simulation tool is used for the study.
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