Boron, fluorine, and carrier profiles for B and BF2implants into crystalline and amorphous Si

摘要

Depth distributions, measured by secondary ion mass spectrometry (SIMS), and carrier profiles, measured by differential capacitancehyphen;voltage (Chyphen;V) profiling, of boron and fluorine implanted as B, F, BF, or BF2ions into random and channeling orientations of crystalline silicon, and into silicon amorphized by silicon ion implantation are reported. Low boron energies of 8 and 10 keV and the corresponding energies of 36 and 45 keV for BF2ions are emphasized because of their use for high resolution device and circuit applications in silicon and siliconhyphen;onhyphen;sapphire. Amorphizing crystalline silicon prior to boron implantation eliminates the significant channeling tails on 8hyphen; or 10hyphen;keV boron profiles. Fluorine penetrates more deeply into crystalline silicon than boron does. Both boron and fluorine redistribute during annealing at 925thinsp;deg;C/20 min for B, F, BF, or BF2implants, but with quite different characteristics as illustrated, and depend on the implantation fluence (5times;1014and 2times;1015cmminus;2reported here). The fluorine redistribution profiles are strongly influenced by the magnitude and distribution of damage that remains after annealing. Fair agreement is shown between boron atom depth distributions measured by SIMS andChyphen;Velectrical profiles measured for a fluence of 1.5times;1012cmminus;2. DifferentialChyphen;Vprofiles indicate that the entire ion spectrum from BF3can be implanted and electrically activated (for a fluence of 1.5times;1012cmminus;2), as can a BF2implant. Implantation through a 20hyphen;nm layer of SiO2has no significant effect on the boron depth distribution in crystalline silicon. Pearson IV moments are given for the low energy boron profiles. The use of these profiles for modeling calculations is discussed. Thesupremmodel of an exponential for the channeling tail of boron implants in crystalline silicon is fairly good for fluences greater than about 1015cmminus;2, but poorer for lower fluences, but the slope and matching to the random portion of the profiles are difficult to predict. In order for modeling calculations to reasonably represent boron profiles, either the silicon substrate should be amorphized prior to boron implantation, or the modeling should be modified to use experimental data measured for the implant and silicon conditions.