Graphite evolution by metal induced crystallization of amorphous carbon on SiNx substrate for extreme ultraviolet pellicles

초록

Graphite is a promising candidate for next-generation extreme ultraviolet (EUV) pellicles due to its high emissivity (>0.3), robust mechanical properties, and ability to achieve high EUV transmission with ultra-thin films (∼30 nm). Traditional chemical vapor deposition methods face challenges like thickness control and transfer-induced damage. To overcome these challenges, we introduced a low-temperature (∼500 °C) metal induced crystallization of amorphous carbon (MICA) for a direct synthesis of uniform graphite on a substrate. We successfully fabricated a 15-nm graphite layer on an 8-inch SiNx/Si wafer through annealing an amorphous carbon (a-C)/Ni bilayer at 500 °C for 1 h. To evaluate the mechanism governing the uniform growth in MICA, we systematically investigated the microstructure evolution of graphite at various annealing temperatures and in various thickness combination of a-C and Ni. Our findings revealed dominantly nucleating graphite at the interface of Ni and a-C. The vertical growth of graphite was controlled by the thickness of Ni. For evaluation of EUV characteristics, the SiNx layer under the graphite was dry etched to make a 15-nm thick graphite membrane, which exhibited an EUV transmittance of 91.56 % and an emissivity of 0.37. Our findings substantiate the feasibility of low-temperature MICA as a promising synthesis method for pellicles.

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