Method of forming a collar using selective SiGe/Amorphous Si Etch
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United States of America Patent
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Jan 17, 2006
Grant Date -
Dec 2, 2004
app pub date -
May 30, 2003
filing date -
May 30, 2003
priority date (Note) -
Expired
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Abstract
A method of forming collar isolation for a trench storage memory cell structure is provided in which amorphous Si (a:Si) and silicon germanium (SiGe) are first formed into a trench structure. An etching process that is selective to a:Si as compared to SiGe is employed in defining the regions in which the collar isolation will be formed. The selective etching process employed in the present invention is a wet etch process that includes etching with HF, rinsing, etching with NH4OH, rinsing, and drying with a monohydric alcohol such as isopropanol. The sequence of NH4OH etching and rinsing may be repeated any number of times. The conditions used in the selective etching process of the present invention are capable of etching a:Si at a faster rate than SiGe.
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