Stanford scientists were able to successfully demonstrate a new directed self-assembly (DSA) process not just for regular test patterns, but for irregular patterns that are required for the manufacture of smaller semiconductors. It was the first time that this next-generation process was used to contact hole patterns at 22 nm, but the scientists claim that the technique will enable pattern etching for next-generation chips down to 14 nm.
"This is the first time that the critical contact holes have been placed with DSA for standard cell libraries of VLSI chips. The result is a composed pattern of real circuits, not just test structures," said Philip Wong, the lead researcher at Stanford for the SRC-guided research. "This irregular solution for DSA also allows you to heal imperfections in the pattern and maintain higher resolution and finer features on the wafer than by any other viable alternative."
The research group also noted that the process is much more environmentally-friendly as a "healthier" solvent - polyethylene glycol monomethyl ether acetate (PGMEA) - is used for the coating and etching process.
Leveraging the new DSA process, the researchers manufactured chips by covering a wafer surface with a block copolymer film and using "common" lithographic techniques to carve structures into the wafer surface and create a pattern of irregularly placed "indentations." These indentations are used to as templates "to guide movement of molecules of the block copolymer into self-assembled configurations." According to the researchers, these templates can be modified in their shape and size, which enables distance between holes to be reduced more than current techniques allow.