Fluorine redistribution and incorporation during solid phase epitaxy of preamorphized Si

Abstract

The redistribution of fluorine during solid phase epitaxial regrowth (SPER) of preamorphized Si has been experimentally investigated, explained, and simulated, for different F concentrations and temperatures. We demonstrate, by a detailed analysis and modeling of F secondary ion mass spectrometry chemical-concentration profiles, that F segregates in amorphous Si during SPER by splitting in three possible states: (i) a diffusive one that migrates in amorphous Si; (ii) an interface segregated state evidenced by the presence of a F accumulation peak at the amorphous-crystal interface; (iii) a clustered F state. The interplay among these states and their roles in the F incorporation into crystalline Si are fully described. It is shown that diffusive F migrates by a trap limited diffusion mechanism and also interacts with the advancing interface by a sticking-release dynamics that regulates the amount of F segregated at the interface. We demonstrate that this last quantity determines the regrowth rate through an exponential law. On the other hand we show that neither the diffusive F nor the one segregated at the interface can directly incorporate into the crystal but F has to cluster in the amorphous phase before being incorporated in the crystal, in agreement with recent experimental observations. The trends of the model parameters as a function of the temperature are shown and discussed obtaining a clear energetic scheme of the F redistribution and incorporation in preamorphized Si. The above physical understanding and the model could have a strong impact on the use of F as a tool for optimizing the doping profiles in the fabrication of ultrashallow junctions

Fluorine effect on As diffusion in Ge

“…1(a)] are three physical phenomena yet showed in Si. [18][19][20][21][22][23][24][25][26]43 V. CONCLUSIONS…”

“…The effect of F in engineering point defects (vacancies and self-interstitials) and, as a consequence, in affecting the diffusion of dopants in Si was extensively investigated by our group, and consists in the annihilation of self-interstitials at nano-bubbles introduced in the crystalline matrix through a complex mechanism of F segregation and incorporation within the crystalline phase. [18][19][20][21][22][23][24][25][26] The aim of this work is to study in detail the effect of F in modifying As diffusion in Ge. For this purpose, we performed structural and chemical characterizations of Ge samples co-implanted with F and As and annealed with different thermal budgets.…”

Investigation of fluorine three-dimensional redistribution during solid-phase-epitaxial–regrowth of amorphous Si

“…Since F is strongly snowplowed by the moving amorphous/crystal interface and the F profile after SPER is significantly different from the implanted one, the redistribution of F during SPER has been matter of intensive investigation, mainly by secondary ions mass spectrometry (SIMS), 10 and a full comprehensive model was elaborated to predict the final F redistribution. 11 This model clearly puts in evidence that F clustering is a crucial step in the F incorporation in c-Si, and it has to be taken into account to correctly reproduce by simulations the F profile during the whole SPER process in a wide range of temperatures (580-700 C). 11 The F clustering during SPER of preamorphized Si has been investigated by transmission electron microscopy (TEM).…”

“…11 This model clearly puts in evidence that F clustering is a crucial step in the F incorporation in c-Si, and it has to be taken into account to correctly reproduce by simulations the F profile during the whole SPER process in a wide range of temperatures (580-700 C). 11 The F clustering during SPER of preamorphized Si has been investigated by transmission electron microscopy (TEM). 12,13 After a partial SPER at 700 C, TEM revealed the presence of cavities both in amorphous Si (a-Si) and in crystal Si (c-Si).…”

“…11. The APT 1D profile was determined by adding the three APT signals (SiF þ , SiF 2 þ , and SiF 3 þ ) since no peak was detected at the expected positions of 1, 2, and 3 times charged F ion that correspond to massto-charge ratios (m/z) of 19.0, 9.5, and 6.3, respectively.…”