Plasma and photon interactions with organosilicon polymers for directed self-assembly patterning applications

Silicon (Si)-containing block copolymers (BCPs) are promising candidates for directed self-assembly patterning applications and are able to access structures with critical dimensions less than 10 nm. Significant etch contrast between the blocks is required to integrate BCPs for patterning applications and form an initial topographical mask. For Si-containing BCPs, O₂ plasma exposure can give high etch contrast between the blocks by forming a thin etch resistant silicon oxide (SiO_x) surface layer from the Si-containing block. The authors have also found that H₂ and N₂/H₂ plasmas can form etch resistant barrier layers from organosilicon polymers (OSPs). Photodegradation of the OSPs induced by H₂ plasma-generated vacuum ultraviolet (VUV) photons initiates the formation of this etch barrier layer. Fourier transform infrared transmission spectroscopy measurements show enhanced VUV-induced degradation in polymers with higher Si content due to cleavage of the methylsilyl bonds (Si-CH₃) and subsequent carbon depletion, leading to formation of an etch resistant Si-enriched surface layer. Furthermore, a dynamic photolysis model based on the dissociation of Si-Si and Si-CH₃ bonds shows that higher Si content in the polymer implies deeper photon penetration. The authors conclude that higher VUV fluxes and higher Si content promote the formation of etch resistant surface barriers on the Si-containing block when dry developing Si-containing BCPs with H₂-rich plasmas. Finally, plasma dry development of an aligned, Si-containing BCP with sub-10 nm domains is demonstrated using a N₂/H₂ plasma.