The Influence of  NH 4 F  on the Etch Rates of Undoped SiO2 in Buffered Oxide Etch

The dependence of etch rates of thermal oxide and undoped vapor‐deposited silicon dioxides as a function of the composition of buffered was examined. The composition of the buffered oxide etch (BOE) was varied from 0–30 weight percent (w/o) ammonium fluoride with 2–15 w/o hydrofluoric acid . The etch rates of the silicon dioxides run through a maximum. The position of the maximum increases linearly to higher concentrations with higher content. For the reaction of dissolution, two different paths are discussed. In BOE with concentration lower than 15 w/o silicon dioxides react mainly with . With higher ammonium fluoride concentration the reaction with becomes increasingly dominant. In BOE with 6 w/o , the activation energy for the reaction of dissolution was determined. Diagrams of etch rates as a function of and concentration are presented.