In this thesis work, chemical kinetics and fluid dynamic behaviour of silicon carbide film growth and nitrogen doping carried inside an industrial Chemical Vapour Deposition reactor, suitable for the production of 150 mm 4H-SiC (0001) circular wafers, have been investigated through numerical simulations conducted with two physical models, one monodimensional and one three-dimensional, implemented in two different softwares; several fixes were applied to the software containing the 1D discretization in an attempt to improve the quality of the simulations. A sensitivity analysis performed at the beginning of this work allowed to identify the key species involved in silicon carbide film growth and nitrogen doping. Subsequently, several optimized monodimensional simulations were launched in order to replicate the experimental trends of growth rate and nitrogen incorporation gathered from two test runs. Lastly, the phenomenon of uneven nitrogen incorporation observed at the lateral zones of the growing silicon carbide wafer was investigated first with a set of simplified monodimensional simulations featuring a fictitious dopant species and then with more detailed three-dimensional simulations; this phenomenon was supposed to be triggered by gas phase reactions converting molecular nitrogen into a dopant intermediate. The outcome of these computations suggests that the reactor could benefit either from a reduction of the wafer’s diameter or by the use of a more efficient dopant precursor.
In questo lavoro di tesi sono stati studiati gli aspetti cinetici e fluidodinamici relativi alla crescita epitassiale, con conseguente drogaggio di azoto, di un film di carburo di silicio tramite deposizione chimica in fase vapore condotta in un reattore industriale utilizzato per la produzione di wafer circolari di 4H-SiC dal diametro di 150 mm; tale reattore è stato modellato in una e in tre dimensioni mediante due differenti software: il software basato sul modello monodimensionale è stato modificato con lo scopo di migliorare la qualità delle simulazioni numeriche. Un’analisi di sensitività condotta all’inizio di questo lavoro ha identificato le specie chiave regolanti il processo di deposizione e drogaggio. Successivamente i dati raccolti da due prove sperimentali sul reattore industriale sono stati riprodotti tramite varie simulazioni monodimensionali ottimizzate dalle modifiche effettuate al software. Infine, l’incorporazione disomogenea di azoto presente nelle zone laterali del wafer di carburo di silicio è stata investigata tramite una serie di simulazioni monodimensionali semplificate con una sola specie dopante fittizia; la formazione di un intermedio di drogaggio ottenuto da azoto molecolare è stata identificata come possibile causa di questo fenomeno. Questa ipotesi è stata successivamente approfondita in una simulazione tridimensionale: il risultato di questa simulazione suggerisce che l’incorporazione disomogenea di azoto potrebbe essere risolta tramite la riduzione del diametro del wafer o utilizzando un precursore di drogaggio più efficiente.
Kinetic and fluid dynamic study of N-doping in SiC chemical vapour deposition
DONINELLI, NICOLÒ
2019/2020
Abstract
In this thesis work, chemical kinetics and fluid dynamic behaviour of silicon carbide film growth and nitrogen doping carried inside an industrial Chemical Vapour Deposition reactor, suitable for the production of 150 mm 4H-SiC (0001) circular wafers, have been investigated through numerical simulations conducted with two physical models, one monodimensional and one three-dimensional, implemented in two different softwares; several fixes were applied to the software containing the 1D discretization in an attempt to improve the quality of the simulations. A sensitivity analysis performed at the beginning of this work allowed to identify the key species involved in silicon carbide film growth and nitrogen doping. Subsequently, several optimized monodimensional simulations were launched in order to replicate the experimental trends of growth rate and nitrogen incorporation gathered from two test runs. Lastly, the phenomenon of uneven nitrogen incorporation observed at the lateral zones of the growing silicon carbide wafer was investigated first with a set of simplified monodimensional simulations featuring a fictitious dopant species and then with more detailed three-dimensional simulations; this phenomenon was supposed to be triggered by gas phase reactions converting molecular nitrogen into a dopant intermediate. The outcome of these computations suggests that the reactor could benefit either from a reduction of the wafer’s diameter or by the use of a more efficient dopant precursor.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/151207