The Feasibility of the Lateral Wet-etching on TiN Layers in 3D Multilayer Stack Structures

The 3D Memory Device is manufactured using vertically multilayer stacked semiconductor structures, based on dielectric materials of Silicon oxide (SiO2) and silicon nitride (Si3N4). Atomic Layer Deposition (ALD) is employed to achieve a homogeneous step coverage of the top surface, sidewalls, and bottom with high aspect ratios to achieve the 3D structure. However, inherent void defects in the lateral pocket layers still exist. The wet chemical lateral etch process, along with preprocess layer seam, results in poor uniformity and profile which significantly affects the storage properties of the device and leads to slower transfer speeds. In this study, a new strategy utilizing Oxide Trim (wet isotropic etching SiO2) has been proposed for wet lateral etching titanium nitride (TiN) thin films deposited by ALD technology to address the seam issue. The trumpet-shaped opening between the stacked layers formed by twice lateral wet-etching Si3N4 promotes inward seam formation after deposition, potentially increasing filler metal density in the seal and improving BL uniformity using wet chemicals with high etching selectivity for TiN to SiO2/Si3N4.