We have established in \autoref{design_rules_lithographic} that our lithographic lower limit is 0.5\um.
Now in this chapter we look at the different etching machines used for determining their minimum line spacing.
\subsection{Poly etching}
Because the "Poly Etcher (DRY-Poly)"(\autoref{poly_etcher_machine}) has minimum line space of 0.5\um we are not limited any further beyond what the lithographic limits are.
The poly layer as well requires a minimum line space of 0.5\um
\subsection{Oxide etching}
Because the "Trion RIE Etcher (DRY-Trion)"(\autoref{trion_RIE_etch_machine}) has no minimum line space defined we are not limited any further beyond what the lithographic limits are.
This means that the oxide etching as well requires a minimum line space of 0.5\um.
This plays into the construction design rules for vias and the like.
When looking at the mask making module "Intertech ISI-2808 Laser Direct Write System" from HKUST (\autoref{mask_maker_machine}) we see the following limitations for the lithographic masks:
\begin{itemize}
\item The Minimum Feature Size of the Laser system is 1.5\um. Any pattern size less than 1.5\um may not come out.
\item The grid of the Laser system is 0.25\um, any off grid pattern will be round off or up to the grid location
\end{itemize}
So the smallest structure \textbf{on the mask} shall be bigger than 1.5\um
If we look at the stepper "ASML Stepper (PHT-S1)" from HKUST(\autoref{lithography_machine}) we see it has a resolution of 0.5\um and a reduction ratio of 5:1
This mean that our feature sizes \textbf{on the wafer} can be around 0.5\um (for sizes below 0.5\um it will require some trickery with multiple overlapping masks in the future)
