Resist coating and developing process technology toward EUV manufacturing sub 7nm node

Abstract

Extreme ultraviolet lithography (EUVL) is getting closer to practical use for mass production every year. For applying EUV lithography to manufacturing, productivity improvement is a critical challenge. Throughput and yield are important factors for productivity. EUV source power is steadily advancing year by year, bringing improvements in throughput. Furthermore, yield improvement is necessary for productivity enhancement. In order to improve the yield in EUV lithography processing, further improvement of defectivity and critical dimension (CD) uniformity is required. Reduction of residue and in-film particle defects is very crucial work to enhance the productivity. For residue defects, it is found that the residue defects detected after development inspection (ADI) are perfectly transferred to after etching inspection (AEI), meaning that high defectivity of residue deteriorates yield directly. Furthermore, in-film particle defect counts increase from ADI to AEI because particles included in spin-on-carbon (SOC) and spin-on-glass (SOG) as well as that in resist film are the sources of defects in AEI, while particles mainly included in resist film can be observed in ADI. Figure 1 shows the normalized defectivity comparison between conventional rinse and filtration used and optimizing rinse used and improving filtration efficiency in ADI and AEI. ADI defectivity in which optimized rinse is applied and improving filtration efficiency achieved 0.04, while that in which conventional rinse and filtration are used defined 1.00, meaning the 96 % of improvement. In addition, AEI defectivity by using optimized rinse and improving of filtration efficiency shows 86 % of reduction as compared with that using conventional rinse and filtration. These results reveal that our novel actions for rinse and material supply show excellent performance for defect reduction. For the other aspect of yield improvement, CD uniformity control is one of the crucial factors. CD variations are comprised of several components such as wafer to wafer CD uniformity, field to field CD uniformity. To achieve CD uniformity target for manufacturing, we have optimized developing process with the latest technology. Then, 15 % of field to field CD uniformity improvement and significant improvement of wafer to wafer CD uniformity are achieved.