Formulations to selectively etch silicon-germanium relative to silicon
Compositions useful for the selective removal by etching of silicon-germanium-containing materials relative to silicon-containing materials, from a microelectronic device having features containing these materials at a surface, the compositions containing hydrofluoric acid, acetic acid, hydrogen peroxide, and at least one additional acid that will improve performance as measured by one or more of an etching rate or selectivity and are tunable to achieve the required Si:Ge removal selectivity and etch rates.
1. A method of selectively removing silicon-germanium from a surface of a microelectronic device relative to a silicon-containing material, the method comprising:
providing a microelectronic device surface that includes silicon and silicon-germanium,
wherein the silicon-germanium has a formula: Si x :Ge y , wherein x is in a range from about 0.70 to 0.90, and y is in a range from about 0.10 to about 0.30, with x+y=1.00,
providing an aqueous etching composition comprising:
from 0.1 to 10 parts by weight hydrogen fluoride,
from 10 to 35 parts by weight dissolved hydrogen peroxide,
from 5 to 50 parts by weight dissolved acetic acid,
from 2 to 40 parts by weight dissolved formic acid,
from 0.1 to 10 parts by weight dissolved sulfuric acid, and
from more than 10 to 20 parts by weight dissolved lactic acid per 100 parts by weight dissolved material in the etching composition,
wherein the aqueous etching composition is provided by combining the hydrogen fluoride, acetic acid, formic acid, sulfuric acid, and optional lactic acid to form a solution followed by combining the hydrogen peroxide and the solution to form the aqueous etching composition; and
contacting the surface with the silicon-germanium-selective etching composition for time and at a temperature effective to selectively remove silicon-germanium relative to the silicon.
2. The method of claim 1 , wherein the etching composition comprises less than 1 part by weight hydrogen fluoride per 100 parts by weight total dissolved materials in the etching composition.
3. The method of claim 1 , wherein the etching composition comprises from 15 to 35 parts by weight dissolved acetic acid 10 to 25 parts by weight formic acid per 100 parts by weight total dissolved materials in the etching composition.
4. The method of claim 1 , wherein the etching composition comprises from 1 to 4 parts by weight dissolved sulfuric acid per 100 parts by weight total dissolved materials in the etching composition.
5. The method of claim 1 , wherein the etching composition comprises from more than 10 to 14 parts by weight dissolved lactic acid per 100 parts by weight total dissolved materials in the etching composition.
6. The method of claim 1 , wherein the etching composition comprises from 10 to 70 weight percent water, per total weight of the etching composition.
7. The method of claim 1 , wherein the surface includes silicon nitride or silicon oxide.
8. The method of claim 1 , wherein the aqueous etching composition comprises less formic acid than acetic acid.