DEEP-SUBMICRON TRENCH PROFILE CONTROL USING A MAGNETRON ENHANCED REACTIVE ION ETCHING SYSTEM FOR SHALLOW TRENCH ISOLATION

One of the important issues for the deep-submicron shallow trench isol ation process is profile control in the trench etch process for voidle ss gap filling with the chemical vapor deposition oxide. We examined t he effects of some additive gases such as N-2 or He-O-2 (30% O-2) on t he trench slope to obtain an optimized trench profile with a commercia l magnetron enhanced reactive ion etching system. It was found that th e thickness of deposited film on the trench sidewall was highly relate d to the trench slope. As the film thickness increases, the trench pro file becomes more tapered. The thickness of the sidewall film was dire ctly proportional to the amount of the additive gases, N-2 and He-O-2. As the amount of He-O-2 increases in the Cl-2+HBr+He-O-2 chemistry, t he etch rate of silicon nitride decreases and the ratio of the silicon etch rate to the silicon nitride etch rate drastically increases. Sca nning electron microscopy shows thick film deposits on the trench side wall during the trench etch process. To know the chemical constituents in the deposited film on the sidewall, an angle-resolved x-ray photoe lectron spectroscopy (XPS) was used. XPS results reveal that the depos ited film on the trench sidewall is composed of SiOx in Cl-2+HBr+He-O- 2 and SiOxNy in Cl-2+HBr+N-2. Cl or Br were not detected in our XPS me asurements because the absorbed Cl or Br might react with water vapor to form HCl(g) or HBr(g) and grow SiOx when the samples are exposed to air. An aspect ratio dependence of the trench sidewall slope was obse rved. Usually the dense patterns are more vertical than the isolated p atterns. (C) 1998 American Vacuum Society.