Three-dimensional memory device with aluminum-containing etch stop layer for backside contact structure and method of making thereof

Abstract

Unwanted erosion of dielectric materials around a backside contact trench can be avoided or minimized employing an aluminum oxide liner. An aluminum oxide liner can be formed inside an insulating material layer in a backside contact trench to prevent collateral etching of the insulating material at an upper portion of the backside contact trench during an anisotropic etch that forms an insulating spacer. Alternatively, an aluminum oxide layer can be employed as a backside blocking dielectric layer. An upper portion of the aluminum oxide layer can be converted into an aluminum compound layer including aluminum and a non-metallic element other than oxygen at an upper portion of the trench, and can be employed as a protective layer during formation of a backside contact structure.