PORTLAND, Ore.—The possible pathways down to the 8-nanometer semiconductor fabrication node were detailed last week at the IEEE
International Symposium on Physical Design (ISPD) in Napa, Calif., albeit through a glass darkly. What's for sure is that the pathway is fraught with engineering peril as three competing technologies tool up for mass production capabilities. However, keynote speaker Burn Lin, a TSMC distinguished Fellow, claimed that one of three alternatives was sure to surmount the downward scaling hurdles to 8-nm design rules.
The three alternative pathways were 193-nanometer immersion lithography supplemented with multi-patterning, extreme ultraviolet (EUV) lithography and e-beam lithography. Immersion is closest to realization, according to Lin, but only if it can surmount spiraling cost barriers. EUV at the 13.5-nanometer wavelength has already been demonstrated capable of sub-20-nanometer design rules, but needs better focusing mechanisms and higher output light sources to overcome reflectivity of optics as low as 65 percent. E-beam is known to be able to achieve the 8-nanometer node today, but is a last-resort technology due to its slow speed and low throughput.
To solve e-beam's throughput problems, Lin described efforts to use massively parallel e-beams at KLA-Tencor Corp. (Milpitas, Calif.) and Mapper Lithography BV (Delft, the Netherlands), allowing thousands of simultaneous beams to speed throughput, albeit only if reliability, uniformity and accuracy can be improved.
One of the best paper nominees at this year's ISPD was from professor Yao-Wen Chang’s group at National Taiwan University, which addressed the overheating problems of massive e-beam writing processes, achieved by reordering the writing sequence to better control dimensional distortions.
One of the invited talks at ISPD was given by research scientist Shayak Banerjee at IBM Research (Austin, Texas) who described how shape tolerance on layout polygons could help advanced node lithography. He also described two manufacturing methods for harnessing these polygons using mask- and layout-optimization.
Mapper Lithography (Delft, the Netherlands) uses more than 10 thousand beamlets operating simultaneously as it aims for migration down to the 8-nanometer node.Source: Mapper Lithography