Formation of Low-Defect-Concentration Polycrystalline Silicon Films by Thermal Plasma Jet Crystallization Technique

Abstract

Defect concentration in polycrystalline silicon (poly-Si) films formed by thermal plasma jet (TPJ) annealing and excimer laser annealing (ELA) has been investigated on basis of the electrical property and spin density (Ns). Phosphorus-doped Si films with an average concentration of 4.3 ×1017 cm-3 and crystallized by TPJ annealing showed electrical conductivity (σ) values of 2.0 ×10-3–7.8 ×10-2 S/cm, whereas ELA Si films show much lower σ values of (1.6–4.5) ×10-6 S/cm regardless of irradiated laser energy density. Ns values in TPJ annealed Si films were (2.3–4.5) ×1017 cm-3, which are roughly one order of magnitude lower than those of ELA films. These results indicate that dangling bonds in crystallized films are the predominant traps and they strongly govern the electrical property. TPJ crystallization offers the possibility of fabricating poly-Si films with a low defect concentration presumably owing to the much lower cooling rate (∼105 K/s) during crystalline growth than that of ELA (∼1010 K/s). By treating TPJ annealed films with hydrogen plasma for 10 min at 250 °C, a defect density as low as 5.0 ×1016 cm-3 is achieved.