Advanced Fabrication of Single-crystal Diamond Membranes for Quantum Technologies

TL;DR

This paper introduces a new, safer method for fabricating large, thin, high-quality single-crystal diamond membranes suitable for quantum technologies, improving reliability and scalability.

Contribution

It presents a novel inductively coupled reactive ion etching process using non-toxic gases to produce smooth, large-area diamond membranes with consistent thickness and improved attachment.

Findings

Membranes are smooth with RMS roughness <1 nm.

Membranes have moderate thickness variation (<1 μm over 200x200 μm²).

Process enhances reliability and scalability of diamond membrane fabrication.

Abstract

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 100 nm 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 SF$_6$. 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 $\approx \,$200x200 $\mu$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 SF$_6$-based processes. Our results thus open the route towards higher reliability in diamond device fabrication and up-scaling.