Filling high aspect-ratio nano-structures by atomic layer deposition and its applications in nano-optic devices and integrations

Abstract

Atomic layer deposition, a highly uniform and conformal deposition process, was utilized to fill trenches of various high aspect-ratio nano-grating structures. Dielectric (e.g., SiO2), metal (e.g., aluminum), and dielectric/metal (e.g., Au∕SiO2) hybrid nano-gratings with a linewidth down to <50nm and an aspect ratio up to 14:1 (700nm:50nm) were trench-filled with various materials particularly nano-laminate materials such as TiO2∕SiO2 and SiO2∕Al2O3. Various high-performance optical devices such as true-zero-order optical retarders (i.e., wave plates) and nanowire-grid polarizers were realized based on an UV-nanoimprint lithography process and the atomic layer deposition for trench fillings. Thanks to both unique material properties and nano-structure trench filling capability, the atomic layer deposition opens a path for innovative nano-structure based optical devices and integrated optical devices.

Conformity and structure of titanium oxide films grown by atomic layer deposition on silicon substrates

“…The conformity studies were performed on the high aspect ratio trenches. In earlier works, the aspect ratios of trenches have been between 1:6.2 [13], 1:20 [14] and 1:12 [15] but in our work deeper trenches (aspect ratio 1:40) in crystalline Si were used. The aspect ratio 1:40 is demanding enough to challenge the deposition process in respect with the pulse/purge ratio.…”

“…TiO 2 has been examined for different applications as a material of conformally grown pure films [13,14], nanolaminates (TiO 2 -SiO 2 , TiO 2 -HfO 2 , TiO 2 -Al 2 O 3 etc.) [15][16][17] or as a constituent material in the processes resulting in the formation of ternary phases e.g. Bi 2 Ti 2 O 7 and AlTiO x [18,19].…”

Effect of atomic layer deposition on the quality factor of silicon nanobeam cavities

“…This effect has already been utilized to grow microlens arrays [14] and planarized optical gratings [15] and to tune photonic crystal waveguides [7,16]. The conformal film also reduces surface roughness, and ALD-grown Al 2 O 3 and TiO 2 films have been found to significantly reduce propagation losses in silicon strip and slot waveguides [13,17].…”

Superconformal chemical vapor deposition of thin films in deep features

“…(4) Atomic layer deposition: ALD can be used to fill or partially fill structures via highly conformal coating. Reports of nominally complete filling include SiO 2 / Al 2 O 3 nanolaminates in vias 27 with AR ¼ 35 and in trenches 28 with AR ¼ 12-14; TiO 2 in V-shaped Si slot waveguides; 11 and Al 2 O 3 in multiwall C nanotubes. 29 Reports of incomplete filling include TiO 2 30 or GaP 31 in opal templates with AR $ 4000 using pulsed gas injection.…”