Etching process in capacitor process of DRAM using a liquid etchant composition

An etching process in a capacitor process of DRAM, comprising:

• providing a substrate that has thereon a silicon layer, a plurality of metal electrodes in the silicon layer, and a cap layer on the silicon layer, wherein the plurality of metal electrodes have outer surfaces, and the outer surfaces are located between the silicon layer and the plurality of metal electrodes;
• removing the silicon layer to form trenches by using a liquid etchant composition, wherein each of the trenches is located between two adjacent metal electrodes and below the cap layer, and the trenches expose the outer surfaces of the plurality of metal electrodes;
• and
• forming a dielectric layer on the outer surfaces of each metal electrodes,
• wherein the liquid etchant composition comprising:
• a main etchant consisting of tetramethylammonium hydroxide (TMAH), consisting of NH4OH, or consisting of TMAH and NH4OH;
• an additive comprising a metal corrosion inhibitor;
• and
• water as a solvent,
• wherein the metal corrosion inhibitor comprises at least one compound selected from the group consisting of diprotic carboxylic acids and phenolic compounds, wherein the phenolic compounds comprise 4-nitrophenol and 4-hydroxybenzoic acid, and the diprotic carboxylic acids comprise malonic acid and succinic acid.