Method for simultaneously forming thinner and thicker parts of a dual oxide layer having varying thicknesses

Abstract

A method for forming a dual oxide layer on a silicon substrate provides that layer having varying thicknesses by using a damage layer formed on the silicon substrate, or a silicon nitride layer deposited on the silicon substrate. The damage layer is formed on the silicon substrate by dry etching a designated part of the silicon substrate, and the dual oxide layer is formed by using the properties of SiO,by which the oxide layer growth speed on the damage layer is slower than that on the silicon substrate. A pattern of the damage layer is defined by photolithography, and the damage layer having a depth of about 20 to 5,000 Å is formed using CF,, CHF,, or Ar gas at a pressure of 900 m Torr or less, or using Cl,or HBr. In the preoxidation cleaning step, a solution containing NH,F, HF, and H,O, a standard solution containing NH,OH, H,O,, and H,O, and/or HF are used. Meanwhile, using the nitride layer, after depositing the silicon nitride to a thickness of about 10 to about 100 Å on the silicon substrate, a pattern of the silicon nitride layer is defined by photolithography and the silicon nitride layer is partially removed depending on the pattern.