Directed self assembly (DSA) of block copolymers is an emerging technology for achieving sub-lithographic resolution.
We investigate the directed self assembly of two systems, polystyrene-block-poly-DL-lactic acid (PS-b-PDLA) and PSb-
poly(methyl methacrylate). For the PS-b-PDLA system we use an open source EUVL resist and a commerciallyavailable
underlayer to prepare templates for DSA. We investigate the morphology of the phase separated domains and
compare the LER of the resist and the PS-PDLA interface. For the PS-b-PMMA system we again use an open source
resist, but the annealing conditions in this case require crosslinking of the resist prior to deposition of the block
copolymer. For this system we also investigate the morphology of the phase separated domains and compare the LER of
the resist and the PS-PMMA interface.
The commercialization of 32 nm lithography has been made possible by using double patterning, a technique that allows
for an increased pattern density, potentially, through resist freezing and high precision pattern registration. Recent
developments in directed self assembly (DSA) also uses resist freezing for stabilizing positive tone resists used in
graphoepitaxy. We have developed a method of patterning an open source, positive tone EUV resist using electron beam
lithography (EBL), and studied a novel way of freezing a positive tone EUV photoresists through electron beam induced
crosslinking. Through metrological analysis, crosslinked pattern was observed to retain consistent critical dimensions
(CD) and line-edge roughness (LER) after they were annealed at temperatures higher than the glass transition of the
photoresist. This process has been used to freeze patterned EUV photoresists, which have been subsequently used for
directed self assembly of PS-b-PMMA and has potential applications in double patterning in an LFLE scenario.
The grafting of polystyrene (PS) onto various polypropylene (PP) containing substrates, previously treated by exposure to a plasma, has been followed by Raman microspectroscopic mapping. The substrates consisted of either pure PP, or blends of PP and ethylene-propylene rubber (EPR). For exactly the same section of polymer surface, Raman spectra were obtained at 1 micrometers intervals for small sections of each substrate, the surface after plasma-treatment, and the surface after PS grafting. Typically, the size of the sections studied was 50 micrometers X 50 micrometers . Raman maps were constructed indicating the crystallinity variation across the surface, and also the distribution of the EPR component in the substrate, and after plasma treatment. Raman maps were also constructed to show the distribution of the PS at the surface after the grafting reaction. Grafting was found to be heterogeneous. The overall amount of grafted PS depended on the amount of EPR in the substrate. For a particular substrate, increased concentrations of grafted PS were correlated with positions on the surface which had higher EPR after plasma treatment.