HIGH-ENERGY CHANNELING IMPLANTS OF PHOSPHORUS ALONG THE SILICON[100] AND SILICON[110] AXES

Phosphorus ions in the energy range 0.25-1 MeV and in the dose range 2 X 10(12)-1 X 10(15) P/cm2 were implanted along the [100] and [110] directions on Si single crystals or along a random direction (7-degrees tilt and 23-degrees twist angles). Some implants were performed also on Si samples with a 2-mu-m-thick surface amorphous layer to obtain truly random conditions. Profiles were obtained either by secondary-ion mass spectrometry or by spreading-resistance analyses after a rapid-thermal-annealing procedure. The presence of channeling tails in the so-called random implants in Si single crystals, due to feeding-in effects, is demonstrated and studied. In the channeling implants, the maximum penetration and the electronic stopping were determined as a function of the beam energy and axial direction. Furthermore, by increasing the implanted dose the dechanneled fraction was correlated with the number of displaced silicon atoms. All the obtained profiles were compared with Monte Carlo simulations using the MARLOWF code. A simple description of the electronic energy loss within different channels by a modified Oen-Robinson formula provided an excellent agreement between the calculated and the experimental profiles.