Atom and carrier depth distributions of beryllium implanted into silicon

The electrical properties and atom depth distributions of Be implanted into Si were studied as a function of implant fluence and annealing parameters. Beryllium depth distributions are presented for eight implant fluences between 2×1012 and 1.5×1016 cm−2. For the lower fluences (⩽1013 cm−2), associated acceptor profiles were measured by differential C-V profiling and were compared with Be profiles obtained by secondary ion mass spectrometry. Two different modes of thermal redistribution of implanted Be are observed, depending upon whether the implants are above or below the amorphization level (∼1.5×1015 cm−2). Acceptor activity was observed for annealing temperatures between 200 and 900 °C. A maximum acceptor density of 8×1016 cm−3 was measured for a 3×1012 cm−2 implanted and 500 °C annealed sample, with ∼50% of the Be being electrically active. Annealing at 600 °C (3×1012 cm−2 implant) resulted in a redistribution of Be with only ∼12% retention; however, the electrical activation of the retained Be was ∼100%. Be implantation of Si substrates held at 200 and 400 °C with no post-implantation annealing produced essentially the same acceptor distributions as room-temperature implanted substrates that were subsequently annealed at the same temperatures.