Densely patterned contact holes form a key component of integrated circuits, but there are significant challenges to patterning holes with a sub 10-nm radius. The directed self-assembly (DSA) of block copolymers offers a potential solution, where a larger hole is initially patterned and a cylinder forming block copolymer (BCP) is assembled inside. The radius of the inner BCP cylinder can now be used to template the hole radius. It can be particularly challenging to characterize the internal structure of the DSA patterned contact hole, particularly for features such as the residual layer, which may adversely impact the etching process. The high aspect ratio of these features makes top-down characterization nearly impossible, forcing the use of challenging cross-section based approaches.
Critical Dimension small angle X-ray scattering (CDSAXS) offers the possibility of characterizing the internal structure of DSA patterned contact holes. CDSAXS is a variable angle scattering technique which combines measurements from different sample angles to reconstruct the three-dimensional structure of the sample. In this case the scattering yields a two-dimensional pattern, where the off-axis peaks contain additional information about the structure. A model based inverse analysis is then used to fit the scattering and evaluate the structure of the measured target. Contact holes were prepared with a variety of radii and surface treatments in order to evaluate which conditions resulted in optimal assembly of the BCP inside the template. The results demonstrate a correlation between hole radius, surface treatment and residual layer thickness.
Daniel F. Sunday, Florian Delachat, Ahmed Gharbi, Guillaume Freychet, Raluca Tiron, and R. Joseph Kline, "Characterizing the internal structure of BCP filled contact holes with critical dimension small angle x-ray scattering (Conference Presentation)," Proc. SPIE 10586, Advances in Patterning Materials and Processes XXXV, 105860X (Presented at SPIE Advanced Lithography: February 28, 2018; Published: 19 March 2018); https://doi.org/10.1117/12.2297480.5754454674001.
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