Doping density, not valency, influences catalytic metal-assisted plasma etching of silicon

• Published in: Materials horizons 2023-08, Vol.1 (9), p.3393-343
• Main Authors: Sun, Julia B, Peimyoo, Namphung, Douglas, James O, Almquist, Benjamin D
• Format: Article
• Language: English
• Subjects: Catalytic activity; Chemical etching; Chemistry; Dopants; Doping; Fluorine; Gas plasmas; Nanoparticles; Plasma etching; Silicon substrates
• ISSN: 2051-6347; 2051-6355
• DOI: 10.1039/d3mh00649b

Metal-assisted plasma etching (MAPE) of silicon (Si) is an etching technique driven by the catalytic activity of metals such as gold in fluorine-based plasma environments. In this work, the role of the Si substrate was investigated by examining the effects of the dopant concentration in both n- and p-type Si and the dopant atom type in n-type Si in SF 6 /O 2 mixed gas plasma. At the highest dopant concentrations, both n- and p-type Si initially exhibit inhibition of the MAPE-enhanced etching. As the etch progresses, MAPE initiates, resulting in catalytic etching of the underlying Si at the metal-Si interface. Interestingly, MAPE-enhanced etching increases with decreasing doping concentrations for both n- and p-type Si substrates, distinct from results for the similar but divergent, metal-assisted chemical etching of silicon in liquid. Our findings show that the metal-Si interface remains essential to MAPE, and surface enrichment of the dopant atoms or other surface chemistries and the size of metal nanoparticles play roles in modulating catalytic activity. Gold catalyses Si etching in dry plasmas via Metal-Assisted Plasma Etching (MAPE). Here, MAPE is shown to be uniquely inhibited by both heavily doped n- and p-type Si, in contrast with reactive ion etching and metal assisted chemical etching (MACE).