Durability to oxygen reactive ion etching enhanced by addition of synthesized bis(trimethylsilyl)phenyl-containing (meth)acrylates in ultraviolet nanoimprint lithography

Abstract

We investigated the selection of bis(trimethylsilyl)phenyl-containing (meth)acrylates as additives to improve the durability to oxygen reactive ion etching (O2 RIE) of sub-50 nm imprint resist patterns suitable for bubble-defect-free UV nanoimprinting with a readily condensable gas. 2,5-Bis(2-acryloyloxyethoxy)-1,4-bis(trimethylsilyl)benzene, which has a diacrylate chemical structure similar to that of glycerol 1,3-diglycerolate diacrylate used as a base monomer, and 3-(2-methacryloyloxyethoxy)-1-(hydroxylethoxy)-2-propoxy-3,5-bis(trimethylsilyl)benzene, which has a hydroxy group similar to the base monomer, were synthesized taking into consideration the Ohnishi and ring parameters, and the oxidization of the trimethylsilyl moiety to inorganic species during O2 RIE. The addition of the latter liquid additive to the base monomer decreased etching rate owing to the good miscibility of the additive in the base monomer, while the addition of the former crystalline additive caused phase separation after UV nanoimprinting. The latter additive worked as a compatibilizer to the former additive, which is preferred for etching durability improvement. The coexistence of the additives enabled the fabrication of a 45 nm line-and-space resist pattern by UV nanoimprinting, and its residual layer could be removed by O2 RIE.

Development of UV-curable liquid for in-liquid fluorescence alignment in ultraviolet nanoimprint lithography

“…The following five successive processes were automatically operated in the imprint stepper. (i) A fluorinated replica mold 29,30) was approached to a resin film on a silica substrate at a speed of 25 µm s −1 until a load cell detected pressure by contact. (ii) Applied pressure was increased to 0.78 MPa.…”

Depth profiles of aluminum component in sequential infiltration synthesis-treated electron beam resist films analyzed by time-of-flight secondary ion mass spectrometry

“…For UV-NIL, we synthesized trimethylsilyl-containing acrylate monomers and investigated the etching durability of the UV-cured resists to oxygen reactive ion etching (O 2 RIE), because the trimethylsilyl groups were oxidized to inorganic silica during O 2 RIE. 25) Although the addition of monomers with trimethylsilyl groups decreased etching rates of UV-cured resins, the etching rates approached to zero by prolonged etching duration probably due to surface segregation of monomers with trimethylsilyl groups. It should be considered that the miscibility of the trimethylsilyl-containing monomers to other monomers brought a limit to formulation of UVcurable resins.…”