The SPIE Advanced Lithography conference this year was dominated by directed self-assembly (DSA). Where in previous years, DSA was confined to one or two sessions, this year we saw DSA papers in many sessions and in all of the parallel conferences (excepting EUV).
As might be expected, there is no “news” in EUV. And in this case, no news is bad news. Indeed, the TSMC plenary report showed that the power level remains unacceptably low, ~10W-20W. (The paper showed a series of “hockey-stick” plots, each one representing future projections from a previous year.) Cymer made no announcements. My conclusion is that mask-makers must expect that multiple patterning (SADP, LELE, etc.) and DSA will dominate in the coming years.
One of the interesting DSA papers was given by IBM: “Customization of DSA patterns from CHEETAH”. CHEETAH stands for chemo-epitaxial etch trim using self-assembled hardmask. The task addressed by this talk was to reduce the overlay requirements of DSA by creating self-aligned lines which can be terminated in the perpendicular direction. That is, IBM have achieved two-dimensional patterning in DSA (lines and cuts) by patterning one self-aligned chemo-epitaxial pattern. If this methodology is shown to be robust, it completely relaxes the overlay requirement within the finest wiring layer, as there is no need for a separate line-cut masking step.
IBM showed impressive micrographs: lines splitting, merging, shifting laterally, and terminating. The contrast with last year’s boringly regular gratings and dot arrays was remarkable. Note that neither this nor any other method to date relieves lithography of the contact/via overlay requirement.
We can expect the proceedings to issue in about four weeks.