Dopant Selective Photoelectrochemical Etching of SiC

Abstract

Single crystalline 4H-SiC is a wide-gap semiconductor with optical properties that are poised to enable new applications in microelectromechanical systems (MEMS) and quantum devices. A number of key hurdles remain with respect to the micro and nano-fabrication of SiC to prepare precise photonic structures with nanometer-scale precision. These challenges include development of a fast, scalable etching process for SiC capable of producing a sub-nanometer roughness semiconductor surface while simultaneously reducing the total thickness variation across a wafer. Our investigation into UV photoelectrochemical processing of SiC reveals high dopant-type selectivity and the advantage of multiple etch stops to reduce layer thickness variation. We demonstrate dopant-type selectivities >20:1 using a single step and a >100x reduction in surface variation by combining two etch stops. Moreover, the etch rate is fast (>4 μm/hr) and the etched surface is smooth (~1 nm RMS). These results demonstrate a scalable path to the fabrication of precise nanoscale SiC structures and electronic devices that will enable the next generation of MEMS and photonic quantum devices.

First-Principles Investigation of Near-Surface Divacancies in Silicon Carbide

“…Additional chemical etching processes with acid solutions, such as HF and piranha, or alkaline solution, such as KOH, have also been used for SiC surfaces, leading to terminations including Si–OH, Si–F, and Si–O–Si , groups. Such solutions are adopted, for example, in photoelectrochemical etching processes to achieve complex patterns as well as undercut photonic structures of SiC. ,, In particular Si–O–Si bridges were found to be the predominant termination for the (2 × 1) reconstruction of the (100) Si-terminated surface when treated with HF and then exposed to O 2 in a controlled manner …”

“…Such solutions are adopted, for example, in photoelectrochemical etching processes to achieve complex patterns 51 as well as undercut photonic structures of SiC. 13,52,53 In particular Si− O−Si bridges were found to be the predominant termination for the (2 × 1) reconstruction of the (100) Si-terminated surface when treated with HF and then exposed to O 2 in a controlled manner. 54 Based on the most common experimental treatments of the SiC surfaces briefly described above and the surface terminations they lead to, here we study the atomistic models presented in Figure 1.…”

Effect of TCS gas flow and pre-etching on homopitaxial growth of 4H-SiC

“…Pre-growth in situ etching with H 2 is one such surface treatment process. [14][15][16] At a certain temperature, using H 2 for in situ etching can eliminate surface scratches, improve substrate surface smoothness, and enhance substrate surface quality. Importantly, through chemical reactions, a layer of SiC is removed from the surface while forming steps.…”