Yusuke Anno

Polymer blends for directed self-assembly

The advantage of blend DSA (Directed Self Assembly) is milder anneal condition than PS-b-PMMA BCP DSA materials and availability of conventional instruments. In this paper, blend type DSA was applied for hole patterning. Target patterns were contact hole and oval hole. Polymer phase separation behavior has been studied from the point of χN. In the case of polymer blend, χN needs to be more than 2 to give phase separation. At first the effect of polymer size was studied. When the polymer weight was low, the shrunk hole was not clean because of low χN. Furthermore, the correlation of shrink amount and χN was studied. Higher χN polymer blend system gave higher shrink amount. High χN polymer systems give clear interface, then the intermixing area would be reduced, then the attached polymer blend part became larger. The polymer blend ratio effect was also investigated. The blend ratio was varied for polymer A/ polymer B=70/30-50/50. The shrink amount of oval hole was reduced with increasing the ratio of polymer B. However, the shrink amount ratio of CDY/CDX was almost constant (~3).

Roughness and variability in EUV lithography: Who is to blame? (Part 1)

Process variability in today’s EUV lithography might be a showstopper for features below 27nm dimensions. At these feature sizes, electrical devices are influenced by quantum effects and thus have to face the discrete behavior of light and matter. More in general, lithography uncertainties arise from each lithographic element: the source, the photomask, the optical system, and the photoresist. In order to individually assess all the different contributions to the final resist roughness, a EUV mask with known absorber pattern variability was used to expose different resists at different process conditions. CD-SEM analyses were performed on both mask absorber and resist pattern and then used to build a stochastic resist model. In this first paper, we present a complete characterization of the root causes which are responsible of the CD nonuniformity for 27nm half-pitch dense contact-holes exposed with the ASML NXE:3100 scanner installed at imec. Using the same stochastic model, a simulated evaluation to quantify the possible impact of the different elements composing the lithographic process is performed at higher numerical aperture.