Contact holes patterning by directed self-assembly of block copolymers: What would be the Bossung plot?

Abstract

Contact hole (CH) patterning by directed-self-assembly (DSA) of polystyrene-b-polymethylmethacrylate (PS-b-PMMA) block copolymers (BCPs) is extensively studied in this paper. Based on statistical analysis performed on 300mm wafers, a process window (PW) for CH shrink is experimentally evaluated in terms of hole open yield and critical dimension (CD) variation after DSA as a function of BCPs of different natural periods and guiding patterns of different dimensions. The PW allowed us to define the suitable BCP molecular weight with the best guiding CD ranges required to achieve a desired DSA hole CD within a specific tolerance. As example, for a DSA hole CD targeted at 19.5 nm with 10% tolerance, circular guiding patterns of 52 nm CD with 20% guiding CD latitude are needed using a 35nm-natural-period BCP. It is also shown that the CH shrink PW is dependent on guiding pattern pitch and on DSA process conditions such as the self-assembly annealing and spin coating conditions. In addition, the study highlights an interesting property of commensurability between guiding pattern dimensions and BCP’s natural period that governs the CH patterning by DSA for both CH shrink and CH doubling configurations. This permits to predict the guiding pattern dimensions needed for CH patterning by DSA using a given BCP of known natural period.