Effect of annealing and oxide layer thickness on doping profile shape of “through-oxide” implanted P+ ions in textured silicon

Phosphorous ions at energies of 60+100 keV, and doses (4+5) x 1015 atom/cm2 have been implanted randomly through SiO2 layers into textured silicon crystals. The penetration profiles of the P+ ions have been determined by means of differential sheet resistivity and Hall-effect, together with the anodic oxidation stripping technique. The effect of the oxide layer thickness and annealing temperature on the junction properties has been studied. The damage produced by implantation has also been investigated using a transmission electron microscope (TEM). From the mobility measurements of the free carriers as a function of depth through the junction, two minima have been observed through oxide implanted samples. The one nearer to the Si SiO2 interface (at about 200 Å from the interface) was related to the damage produced by the recoil oxygen atoms from the oxide layer into silicon. The deeper minimum lies at ∼0.2 μm from the interface and was attributed to the damage produced by the implanted P+ ions, which caused clusters and defect loops after annealing. This damage was observed through TEM photographs. The optimum conditions for producing a shallow junction without losing much of the implanted P+ ions through the oxide layer were estimated.