THE INFLUENCE OF NH4F ON THE ETCH RATES OF LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITION ARSENOSILICATE GLASSES IN BUFFERED OXIDE ETCH

The dependence of the etch rates of low pressure chemical vapor deposition (LPCVD) arsenosilicate glass (AsSG) films with various dopant concentrations as a function of the composition of buffered and unbuffered hydrofluoric acid was examined. The composition of the buffered oxide etch (BOE) was varied from 0-30 weight percent (w/o) ammonium fluoride (NH4F) with 6 w/o hydrofluoric acid (HF), and the concentration of HF from 3-10 w/o HF. In unbuffered hydrofluoric acid the etch rates increase linearly with the HF concentration. In BOE the etch rates run through a maximum. The AsSG films show principally the same etch behavior as undoped films described in a former paper. So we conclude that the same dissolution reaction occurs. A model for the reaction mechanism is proposed.