Buffer oxide etching solution and application thereof in side wall modification of gate oxide layer

The invention provides a buffer oxide etching solution and application thereof in gate oxide layer side wall modification. The etching solution comprises hydrofluoric acid, ammonium fluoride, a surfactant, a thickening agent and ultrapure water. Wherein the surfactant is isomeric alcohol polyoxyethylene ether; and the thickening agent is symmetric polyol ether. Due to the special structure of the used surfactant, the surfactant has good solubility and dispersibility in a fluorine-containing system, low surface tension and low-foam performance are obtained at the same time, and the cleaning effect and uniformity of the surface of the side wall of the gate oxide layer are guaranteed. Due to the characteristic of high viscosity of the thickening agent, the appearance of the smooth side wall is further modified, and excessive corrosion of the side wall is inhibited. The etching solution can effectively inhibit the lateral corrosion of the gate oxide layer, and ensures the completeness and smoothness of the side w