Effect of the tilt angle on antimony in silicon implanted wafers

Abstract

A dose of 5.0×1014 antimony (Sb+) ions cm−2 was implanted into silicon wafers at an energy of 70 keV, at different tilt angles (0°, 15°, 30°, 45°, and 60°). One set of samples was preamorphized with 160 keV germanium (Ge+) ions with a dose of 1×1015 cm−2. The second set consisted of implants into single crystal silicon. After implantation the samples were annealed at 700 °C for 30 s in a pure nitrogen ambient. Secondary ion mass spectroscopy was performed to evaluate the atomic profile and the retained dose as a function of the tilt angle before and after annealing. Rutherford backscattering spectroscopy and ion channeling measurements were performed to quantify the retained dose and the subtitutional fraction of antimony in the preamorphized and crystalline samples. Hall measurements were performed in order to calculate the proportion of the dopant which was electrically active. It was found that the substitutional fraction was a function of the tilt angle for all of the implanted samples. A correlation was also found between the electrical activation and the subtitutional fraction with the highest electrical activation being found at 15° tilt (90% for antimony implants into crystalline silicon) and 0° tilt (94% for antimony implants into amorphous silicon). For all implant angles the substitutional fraction and dopant activation was greater for the implants into amorphized silicon than for those into the crystalline phase.