US Patent 9735151 3D cross-point memory device

The present disclosure generally relates to semiconductor manufactured memory devices and methods of manufacture thereof. More specifically, methods for forming a plurality of layers of a 3D cross-point memory array without the need for lithographic patterning at each layer are disclosed. The method includes depositing a patterned hard mask with a plurality of first trenches over a plurality of layers. Each of the plurality of first trenches is etched all the way through the plurality of layers. Then the hard mask is patterned with a plurality of second trenches, which runs orthogonal to the plurality of first trenches. Selective undercut etching is then used to remove each of the plurality of layers except the orthogonal metal layers from the plurality of second trenches, resulting in a 3D cross-point array with memory material only at the intersections of the orthogonal metal layers.