LabAdviser/Technology Research/Fabrication of Hyperbolic Metamaterials using Atomic Layer Deposition/AZO gratings: Difference between revisions

In order to get rid of the deposited top layer of AZO and to gain access to the Si template core, a pure physical etching with Ar₊ ions (Ionfab 300 plus from Oxford Instruments) was used. Here, the process was tuned to an etch rate of 20 nm/min which provided a well-controlled top layer breakthrough. Following this, the subsequent selective silicon etching (template removal) proceeded using a continuous isotropic etch in a reactive ion etching tool (RIE, from SPTS) based on SF₆ at a substrate temperature of 20°C. The SF₆ gas flow was kept constant at 35 sccm at a process pressure of 80 mTorr. The coil power was set to 30W. This process proceeds with an extreme selectivity towards the deposited AZO without any observable harm on the prepared AZO grating structure. Controlling the etch time is crucial, since prolongation of the etching will result in a collapse of the AZO gratings. 18 min of Si etching was required to fabricate a free standing, separated AZO grating with a minimal amount of the Si core between the AZO lamellas needed to support the grating skeleton.