| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for forming a collar oxide in the trench of a semiconductor substrate by selectively etching a conformal oxide layer. SOLUTION: In a semiconductor substrate 1 having (1) a trench 100, (2) (i) the filler surface demarcated by filler material for partially filling the trench 100, (ii) the upper surface outside the trench 100, and (iii) part of a sidewall of the trench which is not covered by the filler material, and (3) a conformal oxide layer formed on the upper surface, the sidewall, and the filler surface, (a) the substrate 1 is brought into contact with a mixture of hydrogen-containing fluorocarbon and a source of oxygen under the reactive ion etching conditions, and then (b) the substrate 1 is brought into contact with a mixture of fluorocarbon which does not contain hydrogen and gas for dilution under the reactive ion etching conditions, and the upper surface and the filler surface are selectively overetched while most of the conformal oxide is left over on the sidewall of the trench to form a collar oxide 41. |
