US 12,310,020 B2
Three-dimensional memory device including a dummy word line with tapered corner and method of making the same
Nobuyuki Fujimura, Yokkaichi (JP); Shunsuke Takuma, Yokkaichi (JP); Takashi Kudo, Yokkaichi (JP); Satoshi Shimizu, Yokkaichi (JP); and Zhixin Cui, Yokkaichi (JP)
Assigned to Sandisk Technologies, Inc., Milpitas, CA (US)
Filed by SANDISK TECHNOLOGIES LLC, Addison, TX (US)
Filed on Apr. 7, 2022, as Appl. No. 17/715,662.
Prior Publication US 2023/0328981 A1, Oct. 12, 2023
Int. Cl. H10B 43/27 (2023.01); H10B 41/10 (2023.01); H10B 41/27 (2023.01); H10B 41/35 (2023.01); H10B 41/40 (2023.01); H10B 43/10 (2023.01); H10B 43/35 (2023.01); H10B 43/40 (2023.01)
CPC H10B 43/27 (2023.02) [H10B 41/10 (2023.02); H10B 41/27 (2023.02); H10B 41/35 (2023.02); H10B 41/40 (2023.02); H10B 43/10 (2023.02); H10B 43/35 (2023.02); H10B 43/40 (2023.02)] 6 Claims
OG exemplary drawing
 
1. A method of forming a memory device, comprising:
forming a first alternating stack of first insulating layers and first sacrificial material layers located over a substrate, wherein one of the first sacrificial material layers comprises a composite sacrificial material layer including a primary sacrificial material sublayer including a first sacrificial material and a secondary sacrificial material sublayer including a second sacrificial material that is different from the first sacrificial material;
forming a first-tier memory opening through the first alternating stack;
performing an isotropic recess etch process that isotropically etches the second sacrificial material at a higher average etch rate than the first sacrificial material, wherein a recessed sidewall of the composite sacrificial material layer comprises a tapered recessed surface segment; and
forming a memory opening fill structure within a volume including the first-tier memory opening, wherein the memory opening fill structure comprises a vertical stack of memory elements and a vertical semiconductor channel, and comprises a lateral protrusion having a tapered sidewall surface that is parallel to the tapered recessed surface segment.