Plasma Implantation Technology for Upcoming Ultra Shallow and Highly Doped Fully Depleted Silicon On Insulator Transistors

To face the continuous dimensions downscaling for upcoming semiconductor devices, we have investigated a plasma immersion ion implantation way and have compared the results to a conventional one. This new implantation method allows, in particular, high and thin doping concentration to field source and drain requirements for 32 nm node and below. In addition to this key step, a silicon selective epitaxy growth has been performed. Thus, n-type and p-type ion implantations have been carried out on thin blanket SOI substrates in Pulsion (R) plasma ion implantation tool manufactured by Ion Beam Services, with AsH3, BF3 or B2H6 precursors. Then a recrystallization annealing followed by silicon selective epitaxial growth has been performed in a reduced pressure chemical vapor deposition tool. Regarding n-type implantation we observed a poly-silicon growth in areas where the top silicon has been amorphous down to the buried oxide and a mono-silicon growth for areas where the top silicon has not been completely amorphous. Indeed, in this case recrystallization annealing was not sufficient to allow lengthwise solid phase epitaxy growth whereas there were no difficulties for axial one. Regarding p-type implantations no epitaxial growths have been observed at all. This lack of growth cannot be explained by a complete silicon amorphization which would have led to a growth of poly-silicon like for n-type implantation. According to our first results this growth vacancy could be explained by the very high boron atoms concentration on the substrate surface. The latter being resistant to HF-last cleaning could thus block silicon nucleation. However some rinsing processes, more or less aggressive, have been tested to remove this boron silicon alloy layer. Among these different tests, hydrochloric or plasma etching have provided, in some specific cases, promising results allowing an epitaxial silicon growth.