Gate double patterning strategies for 10nm node FinFET devices

Amorphous silicon (a-Si) gates with a length of 20nm have been obtained in a ‘line & cut’ double patterning process. The first pattern was printed with EUV photoresist and had a critical dimension close to 30nm, which imposed a triple challenge on the etch: limited photoresist budget, high line width roughness and significant CD reduction. Combining a plasma pre-etch treatment of the photoresist with the etch of the appropriate hard mask underneath successfully addressed the two former challenges, while the latter one was overcome by spreading the CD reduction on the successive layers of the stack.