Recent progress in understanding ion bombardment-induced synergism in the erosion of carbon due to multispecies impact

Abstract

Multiparticle bombardment-induced synergism in erosion of materials has become a subject of major interest because of its relevance in two important technological developments of recent decades, viz., microelectronics and thermonuclear fusion. Synergistic effects may produce an enhanced erosion of chemically reactive materials (for example, Si, SiO 2, etc, in microelectronics, and C, TiC, etc, in fusion technology) when these are bombarded simultaneously by low energy (⩽1 eV) reactive atoms/molecules and either of energetic (100s to 1000s eV) ions, electrons, or photons. An enhanced erosion is desirable for etching processes in microcircuit fabrication, but it may lead to an undesirably high rate of impurities introduction into fusion plasmas. Results presented here relate only to ion-induced synergistic effects in the erosion of C when simultaneously bombarded by energetic (60 to 5000 eV) H + (D +) ions and sub-eV H° atoms. First results show that synergism may increase the erosion yield of C by factors of ⩾50 to ⩾100 over the yields (~5 × 10 −5 to 10 −3 CH 4/H° due to sub-eV H° bombardment alone, or by factors of ~2 to 3 over the yields (~0.1 CH 4/H +) due to H +−C interaction at the temperature for maximum chemical erosion. Experiments and phenomenological models suggest that ion bombardment-induced damage may play a fundamental role in synergistic erosion.