Sandisk Technologies Inc.

Hiroshi Minakata

Zhixin Cui

Keigo Kitazawa

Yoshiyuki Okura

A three-dimensional memory device includes a first-tier structure containing a first alternating stack of first insulating layers and first electrically conductive layers that has first stepped surfaces, and a first retro-stepped dielectric material portion contacting the first stepped surfaces of the first alternating stack, and a second-tier structure containing a second alternating stack of second insulating layers and second electrically conductive layers that has second stepped surfaces, and a second retro-stepped dielectric material portion contacting the second stepped surfaces of the second alternating stack. The first retro-stepped dielectric material portion has a higher etch rate than the second retro-stepped dielectric material portion. Memory stack structures vertically extend through the first alternating stack and the second alternating stack. Each of the memory stack structures includes a memory film and a vertical semiconductor channel.

Multi-tier three-dimensional memory device containing differential etch rate field oxides and method of making the same

An alternating stack of insulating layers and sacrificial material layers including stepped surfaces is formed over a substrate. After formation of a retro-stepped dielectric material portion over the stepped surfaces, an array of cylindrical openings is formed through the retro-stepped dielectric material portion and the alternating stack. A continuous cavity is formed by isotropically etching the insulating layers and the retro-stepped dielectric material portion selective to the sacrificial material layers. Remaining portions of the retro-stepped dielectric material portion include dielectric pillar structures. A continuous fill material portion is formed in the continuous cavity. Memory stack structures are formed through the alternating stack. The sacrificial material layers and the dielectric pillar structures are replaced with combinations of an electrically conductive layer and a contact via structure. The contact via structures are self-aligned to the electrically conductive layers.

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Yokkaichi, Japan

Hiroshi Minakata