Methods and etchants for etching oxides of silicon with low selectivity

Abstract

A surface having exposed doped silicon dioxide such as BPSG is cleaned with a solution that etches thermal oxide at least one-third as fast as it etches the exposed doped silicon dioxide, resulting in more thorough cleaning with less removal of the exposed doped silicon dioxide. Specific applications to formation of container capacitors are disclosed. Preferred cleaning solutions include about 46 parts ammonium fluoride, about 9.5 parts hydrogen fluoride, and about 8.5 parts ammonium hydroxide in about 100 parts water by weight; and about 670 parts ammonium fluoride and about 3 parts hydrogen fluoride in about 1000 parts water by weight. The latter solution is also useful in cleaning methods in which a refractory metal silicide is exposed to the cleaning solution such as in cleaning prior to spacer formation or prior to a gate stack contact fill, in which case about 670 parts ammonium fluoride and about 1.6 parts hydrogen fluoride in about 1000 parts water is most preferred.