In Plasma ion beam analysis of polymer layer and adsorbed H monolayer etching

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Beam interactions with materials and atoms, 2024-09, Vol.554, p.165439, Article 165439
• Main Authors: Fortier, Louis-Charles, Chicoine, Martin, Chouteau, Simon, Clausse, Mathilde, Lalande, Émile, Lussier, Alexandre W., Roorda, Sjoerd, Stafford, Luc, Terwagne, Guy, Schiettekatte, François
• Format: Article
• Language: English
• Subjects: ERD; In plasma; Ion beam analysis; NRRA; Plasma etching; RBS
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/j.nimb.2024.165439

We present two experiments where a layer is plasma-etched while monitoring its evolution by in plasma ion beam analysis. First, we etch a photoresist with a diffuse O2 plasma at low pressure. Using a 4.335 MeV He beam, Rutherford Backscattering Spectrometry and Elastic Recoil Detection spectra are acquired every minute during 8 h. Etching of most elements follows a linear trend, but H desorbs faster at the beginning of the plasma process, which we ascribe to the ion beam-induced desorption. In addition, we observe a thin Mo layer building up at the surface, likely due to the sputtering of an electrode in the plasma source. Secondly, we etch in HF a crystalline Si (c-Si) sample with surface orientation, which should leave 14 H/nm2 bonded to the c-Si surface. The sample is then introduced in the chamber and exposed to a diffuse Ar plasma at low pressure. During plasma processing, the H surface concentration is monitored using a resonant nuclear reaction with a 15N beam at 6.385 MeV. The initial H concentration is 11.7±1.1 H/nm2, and it decreases over a 3-minute timescale to an equilibrium concentration of 6.0±0.8 H/nm2. Over the range of experimental conditions investigated, the diffuse Ar plasma is therefore not able to entirely sputter the H from the c-Si surface.