Patent ID: 9478557
Filing Date: 2016-10-25
CPC Classification: H01L

Claim Text:
1. A method forming a 3D NAND memory, comprising: (a) forming a multi-layer slab on top of a semiconductor substrate with layers corresponding to structures of an array of vertically aligned NAND strings, the layers including memory layers initially constituted from a first sacrificial material; (b) etching with a trench mask to form trenches spaced apart by ledges in the multi-layer slab; (c) filling the trenches with a second sacrificial material to form filled trenches; (d) providing odd and even masks for respectively providing subarrays of odd and even openings aligned within the filled trenches on top of the multi-layer slab; (e) forming a subarray of odd vertical shafts by etching the second sacrificial material through the odd openings anisotropically and then isotropically; (f) forming odd grottoes by etching isotropically to recess the first sacrificial material at the memory layers such that each odd grotto has walls intruding halfway into a respective adjacent ledge and a grotto opening with jambs of the second sacrificial material in each odd shaft; (g) Removing the jambs by etching through each odd shaft the second sacrificial material isotopically to widen the grotto opening; (h) depositing a layer of word line material in the odd grottoes to form odd socket components of a word lines; (i) depositing a layer of insulating material to line each odd socket component; (j) filling each odd socket component with a floating gate material to form an embedded floating gate; (k) forming odd memory cells and a plurality of odd vertical bit lines through the odd vertical shafts; and (l) repeating (e) (k) with every occurrence of “odd” replaced by “even”, wherein said etching isotropically in (e) removes all the second sacrificial material to create even vertical shafts with a rectangular cross-section hemmed in by a width of the trench and two adjacent odd memory cells and further includes refilling of nitride removed from corners of the even vertical shafts; and said etching isotropically in (f) creates overlapping grottoes with adjoining walls between adjacent pairs of even and odd grottoes in the same memory layer to form a continuous word line with alternating odd and even socket components in a row.