Abstract: There is disclosed an improved method of forming the spacer which isolates the gate conductor from the metal contact with the diffusion (source/drain) region of each array transfer transistor for all memory cells of a DRAM chip. According to the method there is provided a structure consisting of a silicon substrate having a diffusion region formed therein and gate conductor (GC) lines formed thereon. Then, an oxynitride layer and a silicon nitride (Si3N4) layer are conformally deposited in sequence onto the structure by LPCVD in the same tool for total clusterization. Next, the structure is anisotropically dry etched with a chemistry that is Si3N4/oxynitride selective to expose the oxynitride layer between the GC lines and the upper portion thereof in a one step process to form the Si3N4 spacers.

Abstract: A conventional initial deep trench structure consists of a patterned Si3N4 pad layer coated silicon substrate with deep trenches formed therein. The trenches are partially filled with doped polysilicon (POLY1). A dielectric film is interposed between said polysilicon fill and the substrate to create the storage capacitor. A TEOS SiO2 collar layer conformally coats the upper portion of the structure. Now, the TEOS SiO2 is dry etched in a two-step process performed in the same RIE reactor. In the first step, the TEOS SiO2 is etched at least 6 times faster than the Si3N4 (stopping on the Si3N4 pad layer). In the second step, the operating conditions ensure a partially isotropic dry etch, preferably with twice the power and 1.25 times the pressure, thus providing a vertical etch rate 6× the horizontal rate. As a result of this step, the upper part of the silicon substrate in the trench is exposed without damages.