Self-aligned double patterning process for subtractive Ge fin fabrication at 45-nm pitch

• The self-aligned double patterning scheme has been developed to pattern Ge fins.
• To trim CD < 14 nm, an HF wet trimming of SiO2 hard mask has been introduced in the flow.
• Flat etching front, straight profile, and fin depth > 120 nm have been demonstrated.

The self-aligned double patterning scheme has been developed for subtractive Ge fin patterning targeting critical dimension (CD) < 14 nm at pitch of 45 nm. Compared to the Si self-aligned double patterning route, several modifications have been undertaken in different steps of Ge fin pattering, such as hard mask trimming and main etch. Out of several trimming options, it is the wet trim that has been qualified at the final stage of hard mask CD trimming. It allows meeting CD specifications for all structures and keeping straight lines without wiggling. Finally, the Ge main etch chemistry has been developed, which provides not only a straight fin profile but a flat etching front without depth loading attributed to different density structures.