LabAdviser/Technology Research/Fabrication of Hyperbolic Metamaterials using Atomic Layer Deposition/AZO gratings

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 evaluated using cross-sectional scanning electron microscopy (SEM) imaging.

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  Scheme of fabrication flow. High aspect ratio AZO nanograting.

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 Recipe needs to be tuned. Adjusted parameters: temperature, etching and passivation times.	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 Plasma Asher 1
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 Al-doped ZnO (AZO)	Deposition carried at 200oC. Thickness is above 100 nm.	Equipment used: ALD Picosun R200. Standard recipe used: AZO 20T.
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	Ion Beam Etching (IBE).	Opening of deposited AZO top layer using recipe "Ti acceptance" there the stage was placed to 0o degree. The back side of the wafer also needs to be exposed to etching.	IBE/IBSD Ionfab 300
1.9	Scanning Electron Microscopy inspection	By cleaving the sample it is possible to inspect IBE etching results in cross-sectional mode	SEM Supra 1 SEM Supra 2 SEM Supra 3
1.10	Selective etch of Si between ALD AZO coatings.	Si etching proceeds using ICP Metal etcher with isotropic process based on SF6 process gas.	Equipment used: RIE2.
1.11	Scanning Electron Microscopy inspection of fabricated structure.	Proof of final result.	SEM Supra 1 SEM Supra 2 SEM Supra 3