Critical angle of channeling for low energy ion implantation

We investigated the dependence of channeling suppression on wafer tilt angles for sub-5 keV B⁺ and sub-15 keV BF₂ implantations using a ultra-low energy ion implanter. A noticeable reduction of channeling tail for 1 keV B⁺ and 4.5 keV BF₂ implants was demonstrated to require tilt angles greater than 8°. These results are compared with recently published Monte-Carlo simulation data which indicate that ion redistribution at tail region is dominated by channeling along <110> direction with estimated critical angle of 9° for 1 keV B⁺. For boron energy at 3.3 keV, wafer tilt of 8° remarkably suppressed the channeling. We also observed that 15 keV BF₂ implantation, as an equivalent energy of 3.3 keV B⁺, with tilt angle of 4° was sufficient for suppressing the channeling tail in dopant distribution due to additional suppression effect of channeling by implant-induced surface amorphization