Selective etching and polymer deposition on InP surface in CH4/H2-RIE

We conducted a preliminary study of selective etching and polymer deposition for fabricating Bragg gratings with varied depths in InP by using reactive ion etching (RIE) with methane (CH₄). We obtained selectivity in a submicrometer-pitch grating: the InP was etched in the window of the grating in the region with a thick layer, while it was not etched and polymer was deposited in the region without the thick layer. We also found that the selectivity depends on the plasma pressure in RIE.