Advanced Fabrication of Single-Crystal Diamond Membranes for Quantum Technologies

Many promising applications of single crystal diamond and its color centers as sensor platform and in photonics require free- standing membranes with a thickness ranging from several micrometers to the few 100nm range. In this work, we present an approach to conveniently fabricate such thin membranes with up to about one millimeter in size. We use commercially available diamond plates (thickness 50 mu m) in an inductively coupled reactive ion etching process which is based on argon, oxygen and SF6. We thus avoid using toxic, corrosive feed gases and add an alternative to previously presented recipes involving chlorine-based etching steps. Our membranes are smooth (RMS roughness < 1 nm) and show moderate thickness variation (central part: < 1 mu m over approximate to 200 x 200 mu m(2)). Due to an improved etch mask geometry, our membranes stay reliably attached to the diamond plate in our chlorine-based as well as SF6-based processes. Our results thus open the route towards higher reliability in diamond device fabrication and up-scaling.