Surface smoothing of diamond by isotropic plasma atomic layer etching

L. Stockl, C.M. Lewis, M. Huerta, N. Moldovan, R. Divan, S. Miller, L. Stan, A. Sumant
Rowan University,
United States

Keywords: semiconductor


In pursuit of miniaturization within the semiconductor industry, achieving nanometerlevel surface smoothness plays a pivotal role in optimizing device performance and facilitating effective heterointegration. However, smoothing diamond, an ultimate semiconductor with an ultrawide bandgap, poses technological challenges due to its exceptional hardness and chemical inertness. One promising approach involves the removal of material monolayers utilizing atomic layer etching (ALE), leveraging self-limiting reactions for excellent feature depth and variability control. This study investigates the efficacy of an Ar/O2 ALE process on ultrananocrystalline diamond (UNCD) thin-film and single crystal diamond (SCD). A comparative analysis between ALE and O2 reactive ion etching (RIE) on UNCD thin-film revealed that RIE increased root-meansquare (RMS) surface roughness from 8.34 to 15.6 nm, while ALE resulted in a slight reduction from 8.34 to 7.22 nm. Furthermore, a preparation protocol, integrating wet chemical etching and alternating Ar/Cl2 + O2 etch, was implemented on an SCD sample to eliminate surface residues. Subsequent ALE application to the prepared SCD sample indicated surface smoothening; however, more work is needed to optimize ALE etch using Ar/Cl2 + O2 gas chemistry to reduce surface roughness to sub-nanometer levels. Work performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility, was supported by the U.S. DOE, Office of Basic Energy Sciences, under Contract No. DE-AC02- 06CH11357.