Process Characterization of a Load-Locked, Reactive Ion Etching System

We report on process characterization of contact hole etching in a load-locked, hexagonal reactive ion etching system. Contact holes were etched in silicon dioxide and phosphosilicate glass (PSG) with emphasis on wall profile control and selectivity to the underlayer of either single crystal silicon, polysilicon, or aluminum. To achieve these requirements, a two stage etch process was developed. In the first stage, controlled wall taper is obtained with a mixture of CHF3 and O2. The second stage utilizes a mixture of CHF3 and a small amount of CO2 to obtain high selectivity to the underlying material. Evaluation of the effects of chamber pressure, RF power, and gas mixture on taper angle, selectivity, resist erosion, and etch rates is presented. In addition, evidence which suggests that the reproducibility of optimum etch conditions can be enhanced by the use of a continuously pumped process chamber will be discussed.