Damage accumulation in Si during N+ and N-2(+) bombardment along random and channeling directions

Implantation conditions required for the correct study of the molecular eff ect in damage accumulation during light atomic and molecular ion irradiatio n of semiconductors are considered in detail. Disorder production in Si cry stals implanted with 30 keV/atom N+ and N-2(+) ions at room temperature is examined by low angle RES channeling technique. It is found that during irr adiation along a random direction the near-surface damage produced by molec ular ions (N-2(+)) is about twice as much as one produced by atomic ion (N) bombardment. On the other hand, no molecular effect in the near-surface d amage accumulation during irradiation along [111] channeling direction is o bserved. These results are qualitatively explained by subcascade overlap du ring molecular ion implantation. (C) 1999 Elsevier Science B.V. All rights reserved.