Improvements of trench capacitor characteristics by pre-oxidation surface cleaning with HNO/sub 3/-HF-H/sub 2/O solution

A method has been developed for cleaning silicon by slightly etching the surfaces using an HNO/sub 3/-HF-H/sub 2/O solution with an extremely low HF concentration. The method removes near-surface damage and reduces the concentration of heavy metal surface impurities to one tenth that of RCA cleaning. The slight etch method is used for preoxidation cleaning of silicon trenches formed by reactive ion etching. The MOS C-t retention time and the defect density of thermal SiO/sub 2/ in trench capacitors are significantly improved by the cleaning. The method is effective for both trench cleaning and preoxidation cleaning.<>