Dependence of selectivity on plasma conditions in selective etching in submicrometer pitch grating on InP surface by CH{sub 4}/H{sub 2} reactive ion etching
We studied selective etching and polymer deposition in submicrometer pitch gratings on the surface of InP using reactive ion etching with methane and hydrogen and investigated the plasma condition dependence of the selectivity. Using a mask structure consisting of regions with and without a thick layer on a grating-patterned thin layer, we achieved selective etching in submicrometer pitch gratings. In experiments conducted on the same surface at the same time, the InP is selectively etched in the window of the grating in the region with the thick layer, but it is not etched, and polymer is deposited, in the window of the grating in the region without the thick layer. We found that the selectivity depends on the plasma conditions, such as the hydrogen flow rate, pressure, and plasma power in reactive ion etching. This dependence might result from the variation in the ionic atoms of hydrogen or hydrocarbon/hydrogen, which are attracted to the charged mask and supplied to the window of the grating.