David I. Shahin 1, Travis J. Anderson 2, Tatyana I. Feygelson 2, Bradford B. Pate 2, Virginia D. Wheeler 2, Jordan D. Greenlee 2, Jennifer K. Hite 2, Marko J. Tadjer 2, Aristos Christou 1, and Karl D. Hobart 2
1Department of Materials Science and Engineering, University of Maryland — College Park, 2135 Chemical and Nuclear Engineering Bldg. #090, College Park, MD 20742, USA
2Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375, USA
Abstract:
A dry process for selective etching of nanocrystalline diamond thin films has been developed as an alternative to
plasma etching. This process relies on subjecting masked diamond films to a controlled oxygen atmosphere at
temperatures of 700–800 °C to controllably etch both vertically through the film and laterally underneath the
mask. SiO2, SiNx, and Al2O3 films constitute viable mask materials for this process, provided that the underlying
diamond film is fully outgassed before mask deposition and diamond etching. As expected, etching occurred
more rapidly at higher temperatures. The etch rate was higher in the lateral direction than the vertical direction,
which has been attributed to accelerated etching along disordered grain boundaries and the underlying nucleation
layer. Similar activation energies (136–140 kJ/mol) were obtained for both lateral and vertical etching
from 700 to 800 °C. Using the dry etch process developed in this research, diamond films can be removed from
exposed features and undercut masked regions at a controlled rate, as indicated by microscopy and Raman
spectroscopy.