(Color online) Process flow for silicon-mold fabrication using PMMA-b-PMAPOSS as original pattern.
(Color online) Schematic illustration of dry-development process separated into three steps for PMMA-b-PMAPOSS containing spherical PMMA.
Top-view SEM images. (a) PMMA-b-PMAPOSS film on ACL/Si substrate as annealing. (b) and (c) ACL after etching for pattern transfer. The etching applied (b) a multistep method and (c) a single-step method before etching conditions are optimized.
(Color online) Schematic illustration of the etching process applying the multistep method for PMMA-b-PMAPOSS film in the case of PMMA spheres fluctuating perpendicularly to the substrate plane. Left-most illustration shows initial status of film; upper-side illustrations show the process in case of under-etching in first step; lower-side illustrations show the process in case of over-etching in first step.
(Color online) Cross-sectional illustration of (a) PMMA-b-PMAPOSS film in initial status and (b) holes after etching of the film. All dimensions are defined and represented in the illustrations.
(Color online) Time dependence of hole-diameter of the etching process for PMMA-b-PMAPOSS film. ta is the time point at which the upper PMAPOSS layer is etched completely; tb is the time point at which the PMMA sphere is etched completely; tc is the time point at which the lower PMAPOSS layer is etched completely; td is the time point at which lower PMAPOSS layer is over-etched to a standard endpoint.
Dependence of hole-diameter on variation of PMMA sphere position [(a) and (b)]; dependence of hole-diameter on variation of PMMA sphere diameter [(c) and (d)]. Variation is converted to relative standard deviation. (a) and (c) change of the dependence with s without modification of a. (c) and (d) change of the dependence with a without modification of s.
Dependence of defect rate on processing-time. The defects are no-opening defect, connecting defect, and total number of defects. The processing-time is normalized.
Top-view SEM images of PMMA-b-PMAPOSS film on ACL/silicon substrate. Etching was applied by (a) single-step method before optimization of conditions and by (b) single-step method after optimization of conditions.
Dependence of defect ratio on RSD of PMMA sphere or position. Dashed line and solid line represent calculation result and experimental result, respectively. Blue lines are the result of applying the nonoptimized condition. Red lines are the result of applying the optimized condition.
Cross-sectional SEM image of the holes that formed in the silicon substrate after pattern transfer. Dimensions in the image are mean values of ten holes.
(Color online) (a)–(d) Top-view SEM images. PMMA-b-PMAPOSS (BCP) film (a) without DSA process using chemically patterned template, (b) with DSA process. Silicon substrate (c) processed without DSA and (d) with DSA process. (e) and (f) Dot-size distribution of initial BCP and pattern transferred silicon substrate. RSD of dot/hole-diameter of (a)–(d) are 15, 15, 24, and 16%, respectively.
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