CNR ExploRA

Articolo in rivista, 2023, ENG, 10.1021/acs.langmuir.3c01652

Native Silicon Oxide Properties Determined by Doping

Michele Della Ciana, Alessandro Kovtun, Caterina Summonte, Andrea Candini, Daniela Cavalcoli, Denis Gentili, Roberta Nipoti, and Cristiano Albonetti

Michele Della Ciana - Consiglio Nazionale delle Ricerche - Istituto per lo Studio dei Materiali Nanostrutturati (CNRISMN), 40129 Bologna, Italy; Present Address: SACMI Imola, Via Selice Provinciale 17/A, 40026 Imola, Italy Alessandro Kovtun - Consiglio Nazionale delle Ricerche - Istituto per la Sintesi Organica e la Fotoreattivita? (CNRISOF), 40129 Bologna, Italy; orcid.org/0000-0002- 7614-7100 Caterina Summonte - Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), 40129 Bologna, Italy Andrea Candini - Consiglio Nazionale delle Ricerche - Istituto per la Sintesi Organica e la Fotoreattivita? (CNR-ISOF), 40129 Bologna, Italy; orcid.org/0000-0003-3909-473X Daniela Cavalcoli - Department of Physics and Astronomy, University of Bologna, 40127 Bologna, Italy; orcid.org/ 0000-0002-2417-1248 Denis Gentili - Consiglio Nazionale delle Ricerche - Istituto per lo Studio dei Materiali Nanostrutturati (CNR-ISMN), 40129 Bologna, Italy; orcid.org/0000-0002-7599-2804 Roberta Nipoti - Consiglio Nazionale delle Ricerche - Istituto per la Microelettronica e Microsistemi (CNR-IMM), 40129 Bologna, Italy

ABSTRACT: The physico-chemical properties of native oxide layers, spontaneously forming on crystalline Si wafers in air, can be strictly correlated to the dopant type and doping level. In particular, our investigations focused on oxide layers formed upon air exposure in a clean room after Si wafer production, with dopant concentration levels from ?1013 to ?1019 cm-3. In order to determine these correlations, we studied the surface, the oxide bulk, and its interface with Si. The surface was investigated using the contact angle, thermal desorption, and atomic force microscopy measurements which provided information on surface energy, cleanliness, and morphology, respectively. Thickness was measured with ellipsometry and chemical composition with X-ray photoemission spectroscopy. Electrostatic charges within the oxide layer and at the Si interface were studied with Kelvin probe microscopy. Some properties such as thickness, showed an abrupt change, while others, including silanol concentration and Si intermediate-oxidation states, presented maxima at a critical doping concentration of ?2.1 × 1015 cm-3. Additionally, two electrostatic contributions were found to originate from silanols present on the surface and the net charge distributed within the oxide layer. Lastly, surface roughness was also found to depend upon dopant concentration, showing a minimum at the same critical dopant concentration. These findings were reproduced for oxide layers regrown in a clean room after chemical etching of the native ones.

Langmuir (Online) 39 , pp. 12430–12451