Ion implantation of boron into silicon by use of the boron cathodic-arc plasma generator: First results

A high fluence of boron (B) has been ion implanted into Si by use of a B cathodic-arc plasma generator. The purpose was to demonstrate the viability of the technique for B p-doping. Operation of a pure solid B cathode in a cathodic arc depends on a patented technique for consolidation of the cathode. The target sample ({1 0 0} semiconductor Si) was contained within an exposed area of some 10 cm2, upon which the effective pure B+ ion current was about 30 mA/cm2 for a total effective B+ current of 300 mA. The 100% singly ionized B plasma contained virtually no non-boron ions, molecular radicals or neutral atoms. The arrangement was of the PIII type within the forward projecting plume, with bias of −500 V. The applied fluence was 3.5 × 1017/cm2 divided on to two pulses of 1 s each. Analysis was primarily by RBS/ion channeling and by the 11B(p, α)8Be reaction. The retained dose was 6.1 × 1016/cm2 or about 18% of the applied fluence. If sputter saturation is assumed, the implied sputter yield is 0.3, a value that agrees with the TRIM-calculated yield at saturation. Amorphization depth was 9.2 nm including the oxide and 8.4 nm if Si in the SiO2 is subtracted. Etching with HF reduced the retained B to 4.5 × 1016/cm2. Macroparticle filtering was unsophisticated. Macroparticles adhering were 1500/cm2 for this high applied dose. That value would scale to 1/cm2 for an applied dose of 2 × 1014/cm2. Expansion of the plume to larger areas and other parameter changes will allow adaptation of the technique to shallow junction and other p-doping.