LabAdviser/Technology Research/Fabrication of Hyperbolic Metamaterials using Atomic Layer Deposition/TIO ALU Gratings Procces flow

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This page is written by Evgeniy Shkondin @DTU Nanolab if nothing else is stated.
All images and photos on this page belongs to DTU Nanolab and DTU Electro (previous DTU Fotonik).
The fabrication and characterization described below were conducted in 2013-2016 by Evgeniy Shkondin, DTU Nanolab.

Procces flow description

All samples were prepared and characterized in a class 100 cleanroom. Si (100) wafers of 150 mm were used as a substrate. The main steps in the gratings manufacturing are shown in a figure below. First, the silicon trenches were realized by deep reactive ion etching (DRIE). Then, the trenches were ALD coated. After the selective removal of the top parts, the silicon core between ALD coatings was etched away during the last step. The final structure represents the highly anisotropic vertical grating. Each fabrication step was carefully inspected using cross-sectional scanning electron microscopy (SEM) imaging.

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  Scheme of fabrication flow. High aspect ratio Al₂O₃ and TiO₂ nanogratings.

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  High aspect ratio Al₂O₃ and TiO₂ nanogratings. SEM cross-sectional inspection.

Process flow

Description of steps for fabrication of TiO₂ and AL₂O₃ nanogratings.

Step		Description	LabAdviser link	Image showing the step
1.1	Plasma surface treatment	To ensure clean surface, the 100 mm Si wafer is treated by O2/N2 plasma. (Optional step)	Plasma Asher 2
1.2	DUV Resist patterning	DUV	DUV Stepper Lithography.
1.3	Deep reactive ion etching (DRIE)	DRIE; Recipe: PolySOI10	DRIE Pegasus.
1.4	Plasma surface treatment	To ensure that remainings of DUV resist are gone, samples are treated by O2/N2 plasma. (Optional step)	Plasma Asher 2.
1.5	Scanning Electron Microscopy inspection	By cleaving the sample it is possible to inspect DRIE etched Si trenches in cross-sectional mode	SEM Supra 1 SEM Supra 2 SEM Supra 3
1.6	Atomic Layer Deposition of either Al2O3 or TiO2	Deposition carried at 150C.Thickness is 90 nm.	Equipment used: ALD Picosun R200. Standard recipes used: Al2O3T and TiO2T .
1.7	Scanning Electron Microscopy inspection	By cleaving the sample it is possible to inspect ALD coatings deposited on Si trenches in cross-sectional mode	SEM Supra 1 SEM Supra 2 SEM Supra 3
1.8	Opening of deposited Al2O3 or TiO2 top layers.	Etching happens using ICP Metal etcher with Cl2/BCl3 process gasses.	Equipment used: Metal ICP Etcher.
1.9	Scanning Electron Microscopy inspection	By cleaving the sample it is possible to inspect ICP etcher results Si trenches in cross-sectional mode	SEM Supra 1 SEM Supra 2 SEM Supra 3
1.10	Selective etch of Si between ALD Al2O3 or TiO2 coatings.	Si etching proceeds using ICP Metal etcher with isotropic process based on SFf process gas.	Equipment used: Metal ICP Etcher.
1.11	Scanning Electron Microscopy inspection of fabricated structure.	Proof of final result.	SEM Supra 1 SEM Supra 2 SEM Supra 3
1.12	Ion beam etching. (Optional)	Additional shape of the top part. 20 mijn etch using recipe "Ti acceptance" there the stage shoud be placed to 0o degree. SEM cross section is used for inspection	IBE/IBSD Ionfab 300