Patent ID: 8895437

Claim:
A method of forming a staircase word line in a 3D memory for accessing memory elements arranged in a three-dimensional pattern defined by rectangular coordinates having x, y and z-directions and with a plurality of parallel planes stacked in the z-direction, said method includes forming plane by plane a slab of the plurality of parallel planes, comprising: (a) depositing a layer of word line material in an x-y plane; (b) cutting a pattern of trenches in the layer of word line material with a first mask, the trenches extending along the y-direction and are spaced apart in the x-direction for isolating the layer of word line material into word line segments; (c) filling the trenches with oxide; (d) depositing a layer of oxide above the layer of word line material followed by planarization; (e) cutting a second pattern of trenches in the layer of oxide with a second mask for isolating the layer of oxide into oxide segments, the second mask being identical to the first mask but offset from the first mask in the x-direction by a predetermined offset such that the one end of each word line segment is exposed for connection to a layer of word line material to be formed in the next plane; and repeating (a)-(e) for the next plane except the first mask is offset by the predetermined offset from the second mask of a previous plane such that one end of each oxide segment is exposed for connection to a layer of oxide material to be formed in the next plane.