Channeling Analysis and Electrical Behavior of Boron Implanted Silicon

Abstract

The depth distribution and the lattice location of boron atoms and their correlations with defects and effective carriers in heavily boron implanted silicon have been studied by means of channeling analysis and electrical measurements with a successive layer removal technique. The same set of crystals was used, which had been implanted with boron ions of 100 keV to doses of 1 x 10¹⁶/cm² at room temperature. The ¹¹B(p,α)⁸ Be reaction was utilized to obtain the boron distribution and to determine the lattice location of boron atoms. The angular dependences of the yields of the (p,α) reaction around the <111>, <110> and <100> axes were measured after annealing at 900°C with non-etched, 2950 Å etched, and 3750 Å etched samples. Main results obtained are the following: 1) Boron atoms which exceed the solubility limit, precipitate parallel to the <110> direction in the region of the highest concentration of boron atoms after annealing at 700-900°C. This is also confirmed by the facts that the distribution of the secondary defects coincides with that of boron and that the percentage of the electrically active boron is significantly lower around the boron ion range. 2) The boron distribution does not change significantly after annealing up to 900°C. A considerable diffusion of boron atoms was detected after annealing at 1000°C. In the temperature range from 900°C to 1000°C, the precipitated boron atoms are released and diffuse to become electrically active. 3) The depth distribution of boron atoms deviates from a gaussian. The projected ion range is approximately 20% shorter than the value calculated from the LSS theory.