ASPECT RATIO-DEPENDENT ETCHING ON METAL ETCH - MODELING AND EXPERIMENT

In process development for submicron and sub-half-micron metal etch, e tching rates have been observed to depend on aspect ratio of microstru ctures. Three major mechanisms, including neutral transport, ion trans port, and inhibitor deposition into high aspect ratio features and on open areas, were modeled to interpret the aspect ratio dependent etchi ng (ARDE) phenomena and to explain the experimental results. It is fou nd that the ARDE is mainly controlled by the ion to neutral flux ratio and ion to inhibitor flux ratio. The increase of ion to neutral flux ratio will exaggerate the normal reactive ion etching (RIE) lag. The d ecrease of ion to inhibitor flux ratio tends to make a reverse RIE lag . Both model and experiment indicate that the appropriate ion to neutr al flux ratio and ion to inhibitor flux ratio are the key in minimizin g the ARDE and reducing the microscopic nonuniformity. (C) 1996 Americ an Vacuum Society.