Contact holes patterning by directed self-assembly of block copolymers: process window study

Abstract

Contact hole (CH) patterning by directed self-assembly (DSA) of polystyrene-b-polymethylmethacrylate (PS-b-PMMA) block copolymers (BCPs) is extensively studied. Based on statistical analysis of defectivity and CD measurements after DSA, a process window (PW) for CH shrink is experimentally determined as a function of guiding pattern dimensions and BCP molecular weights corresponding to BCP natural periods. This PW permits to define the suitable BCP molecular weight and the best guiding CD ranges required to achieve a desired DSA hole CD within a specific tolerance. As an 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 35-nmnatural-period cylindrical BCP. Furthermore, it is shown that the CH shrink PW is also dependent on the guiding pattern density and the DSA process conditions such as the self-assembly annealing and the spin coating conditions. The study also highlights an interesting property of commensurability between guiding pattern dimensions and BCP's natural period that governs the DSA CH patterning for both CH shrink and CH doubling configurations. This permits one to predict the guiding pattern dimensions needed for CH patterning by DSA using a given BCP of known natural period.

Balancing Block Copolymer Thickness over Template Density in Graphoepitaxy Approach

“…Indeed, according to Figure 6a, the BCP fills about 40% and 96% of the guiding cavity at 110 and 250 nm pitches, respectively, which confirms the BCP thickness variation with guiding pattern density when using the standard DSA graphoepitaxy process. Accordingly, the HOY, defined as the ratio of valid shrunk holes to total inspected holes, [34] reaches 100% for the most dense patterns but it drastically decreases down to zero when the guiding pattern pitch increases (Figure 6b). On the other hand, using the planarization process, the remaining BCP film thickness inside the cavity after etch-back is still constant over the pitch and thus the HOY is at 100% for all the guiding pattern densities.…”

“…The DSA process employed in this paper is based on the graphoepitaxy approach using organic hard mask guiding patterns . The guiding patterns were generated on 300 mm substrate wafers using a standard trilayer stack composed of a resist, SiARC, and spin on carbon (SOC).…”

“…Measurements were done over 100 contacts per chip on 70 chips on the wafer (≈7000 total inspected contacts per pattern) using the methodology described in ref. . BCP film thickness inside contact‐holes was determined via step height measurements using an Insight3D AFM from Bruker.…”

“…The DSA process employed in this paper is based on the graphoepitaxy approach using organic hard mask guiding patterns. [3,34,35] The guiding patterns were generated on 300 mm substrate wafers using a standard trilayer stack composed of a resist, SiARC, and spin on carbon (SOC). Various circular test structures with different dimensions, pitches for contact-hole shrink applications were designed in the electron sensitive resist by e-beam lithography on a VISTEC SB3054DW tool working at an accelerating voltage of 50 kV and a current density of 20 A cm −2 .…”

Dynamic behavior in self-assembly process of cylindrical phase PS- b -PMMA block copolymer

“…One of the most useful approaches for implementation of DSA is via patterning through templated DSA (grapho-epitaxy) since hole patterns are readily accessible through templated hole patterning of cylindrical phase BCP materials. Many studies were presented by several groups [39][40][41][42] for contact hole shrink by directed self-assembly on 300 mm pilot line processing where holes size below 20 nm with 10% tolerance were achieved. …”