Plasma induced charging damage on thin gate oxide

The plasma damage of gate oxides with the thickness of 45 and 35 Å was investigated using NMOS and PMOS devices with poly-Si antennas. Poly etch was performed in a magnetically enhanced reactive ion etcher (MERIE) reactor using Cl₂/HBr chemistry. The transistors in the antenna test pattern had the antenna ratio of 5000:1. Among the antenna patterns used in this study, the comb type antenna devices suffered more from charging damage during poly-Si etching. Two different methods of wet and NO type were employed to grow the gate oxides. The wet and NO gate oxides were grown in O₂+H₂ and O₂ ambient followed by NO anneal, respectively. In the bar type antenna pattern with the small length/width ratio (dummy antenna), the dependences of plasma damage on poly-Si etching, ion implantation and annealing conditions were not observed, However evident charging damage behavior is observed in the NMOS transistors having comb antenna, which were affected more by charging damage during poly-Si etching. The results of plasma damage characterization indicated that the device structure with amorphous Si (grain size:3000 Å) on NO gate oxide is more resistent to the plasma damage than that of fine grain Si (grain size:300 Å) on wet gate oxide