Publication

Monolayer Doping of Silicon through Grafting a Tailored Molecular Phosphorus Precursor onto Oxide-Passivated Silicon Surfaces

Résumé

Monolayer doping (MLD) of silicon substrates at the nanoscale is a powerful method to provide controlled doses of dopants and defect-free materials. However, this approach requires the deposition of a thick SiO2 cap layer to limit dopant evaporation during annealing. Here, we describe the controlled surface doping of thin oxide-passivated silicon wafers through a two-step process involving the grafting of a molecular phosphorus precursor containing a polyhedral oligomeric silsesquioxane (POSS) scaffold with silica-like architecture and thermal annealing. We show that the POSS scaffold favors the controlled formation of dopant-containing surface species with up to similar to 8 x 10(13) P atoms cm(-2) and efficiently avoids phosphorus evaporation during annealing for temperatures up to 800 degrees C. Silicon doping is demonstrated, in particular, by grafting the POSS phosphorus triester on SiO2/Si wafers with optimized surface preparation (thin SiO2 layer of 0.7 nm) and annealing temperature (1000 degrees C), which provides phosphorus doses of similar to 7 x 10(12) P atoms cm(-2) in the silicon substrates together with a decrease of their sheet resistance. A detailed study of the surface chemistry on SiO2 nanoparticles used as a high-surface-area model yields the grafting mechanism and the structure of the surface species. We show that the POSS scaffold is conserved upon grafting, that its size controls the final P-surface density, and that it behaves as a self-protecting ligand against phosphorus volatilization during the annealing step. We thus demonstrate that the use of custom-made dopant precursors with self-capping properties is a promising approach to tune medium to low doping doses in technologically relevant semiconductors.

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Concepts associés (31)
Dopage (semi-conducteur)
Dans le domaine des semi-conducteurs, le dopage est l'action d'ajouter des impuretés en petites quantités à une substance pure afin de modifier ses propriétés de conductivité. Les propriétés des semi-conducteurs sont en grande partie régies par la quantité de porteurs de charge qu'ils contiennent. Ces porteurs sont les électrons ou les trous. Le dopage d'un matériau consiste à introduire, dans sa matrice, des atomes d'un autre matériau. Ces atomes vont se substituer à certains atomes initiaux et ainsi introduire davantage d'électrons ou de trous.
Crystalline silicon
Crystalline silicon or (c-Si) Is the crystalline forms of silicon, either polycrystalline silicon (poly-Si, consisting of small crystals), or monocrystalline silicon (mono-Si, a continuous crystal). Crystalline silicon is the dominant semiconducting material used in photovoltaic technology for the production of solar cells. These cells are assembled into solar panels as part of a photovoltaic system to generate solar power from sunlight. In electronics, crystalline silicon is typically the monocrystalline form of silicon, and is used for producing microchips.
Silicium
Le silicium est l'élément chimique de numéro atomique 14, de symbole Si. Ce métalloïde tétravalent appartient au groupe 14 du tableau périodique. C'est l'élément le plus abondant dans la croûte terrestre après l'oxygène, soit 25,7 % de sa masse, mais il n'est comparativement présent qu'en relativement faible quantité dans la matière constituant le vivant.
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Learn the fundamentals of microfabrication and nanofabrication by using the most effective techniques in a cleanroom environment.
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