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Y. Nakamura et al., Journal of Vacuum Science & Technology A 25, 1062 (2007) https://doi.org/10.1116/1.2713114, To develop 32 nm node devices, the degradation of atomic layers on the surface of Si substrates must be controlled. During the etching of a Si O2 or Si3 N4 hard mask or sidewall, the surface of Si is attended due to exposure to fluorocarbon plasma. The authors have quantitatively evaluated the relationship between the energy of incident ions and the thickness of the fluorocarbon polymer for a C H2 F2 C F4 Ar O2 plasma in a dual frequency CCP system. At a fixed ion energy the thickness of the damage layer (Td) basically depended on the thickness of the fluorocarbon polymer (TC-F). When the TC-F was changed by controlling the OC Fx gas ratio, Td had a minimum thickness under the conditions at balance point: Pb, under which the TC-F was nearly equal to ion penetration depth: Dp. Using molecular dynamics simulation, reaction around the transition from Si O2 to Si was clarified. The damage was done to the Si before the Si O2 was completely removed, and the largest Td was observed when the Si O2 was etched off. After that, TC-F began to increase because there was no longer an outflux of O from Si O2 and the damage decreased as the unstable Si Fx species in the damaged layer desorbed. Once the TC-F became thicker than the ion penetration depth, the damaged layer got buried and Td stopped changing. When the ion penetration depth was controlled to be equal to TC-F in a steady state under low ion energy conditions, the Td was reduced to less than 1 nm. © 2007 American Vacuum Society.

Changes in chemical nature of an ArF photoresist caused by various plasmas were analyzed, and it was found that the HBr plasma treatment induces a selective detachment of a heterocyclic unit of the photoresist, and the detached unit remains in the photoresist film. Thermomechanical analyses were performed, which showed that the softening temperature of the photoresist decreases by the HBr treatment, indicating that the detached heterocyclic unit acts as a plasticizer in the photoresist film. These results showed that the HBr treatment can be regarded as a softening process of the photoresist. This HBr treatment was applied to the fabrication of line patterns and it was shown that the treatment remarkably improves LWR (line width roughness) after etching. This improvement was more pronounced for the case of an isolated pattern than the case of a dense pattern. Further investigations on the HBr treatment were performed by changing the copolymerization ratio of a monomer containing the heterocyclic unit. It was shown that the reduction of LWR by the HBr treatment becomes more enhanced when the copolymerization ratio increases. However, an intensive HBr treatment was found to deteriorate LWR, showing that there is an optimum condition of the HBr treatment in terms of improving LWR.