Method for forming a self-aligned buried strap in a vertical memory cell

摘要

A method for forming a self-aligned buried strap in a vertical memory cell. A semiconductor substrate with a trench is provided. A collar dielectric layer is conformally formed on the trench bottom portion, and the trench is filled with a conducting layer. The collar dielectric layer is etched below the level of the surface of the conducting layer to form a groove between the conducting layer and the trench. The groove is filled with a doped conducting layer. The dopant in the doped conducting layer is diffused to the semiconductor substrate in an ion diffusion area as a buried strap. The conducting layer and the doped conducting layer are etched below the ion diffusion area. A top trench insulating layer is formed on the bottom of the trench, wherein the top trench insulating layer is lower than the ion diffusion area.