Three-dimensional memory device containing direct contact drain-select-level semiconductor channel portions and methods of making the same
An alternating stack of insulating layers and word-line-level spacer material layers is formed over a substrate. Memory opening fill structures including a respective memory film, a respective word-line-level semiconductor channel portion, a respective word-line-level dielectric core laterally, and a respective sacrificial dielectric material portion are formed through the alternating stack. Drain-select-level material layers are formed over the alternating stack and the memory opening fill structures. Drain-select-level openings are formed through the drain-select-level material layers and over the memory opening fill structures. The sacrificial dielectric material portions are removed selective to the word-line-level semiconductor channel portions underneath the drain-select-level openings. Drain-select-level semiconductor channel portions are formed directly on a respective one of the word-line-level semiconductor channel portions.
1. A three-dimensional memory device comprising:
an alternating stack of insulating layers and word-line-level electrically conductive layers located over a substrate;
a memory opening vertically extending through the alternating stack;
a memory opening fill structure located within the memory opening and comprising a memory film, a word-line-level semiconductor channel portion laterally surrounded by the memory film, and a word-line-level dielectric core laterally surrounded by the word-line-level semiconductor channel portion; and
a drain-select-level pillar structure overlying the memory opening fill structure and comprising a cylindrical gate electrode, a gate dielectric, a drain-select-level semiconductor channel portion, a drain-select-level dielectric core that is laterally surrounded by the drain-select-level semiconductor channel portion, and a drain region contacting an upper end portion of the drain-select-level semiconductor channel portion and having a doping of an opposite conductivity type than the drain-select-level semiconductor channel portion and the word-line-level semiconductor channel portion, wherein an interface between the drain-select-level semiconductor channel portion and the word-line-level semiconductor channel portion is vertically coincident with an interface between the word-line-level semiconductor channel portion and the word-line-level dielectric core, and a lower end portion of the drain-select-level semiconductor channel portion is located between the drain-select-level dielectric core and the word-line-level dielectric core.
2. The three-dimensional memory device of claim 1 , further comprising an insulating cap layer overlying the alternating stack, wherein a vertical interface between the drain-select-level semiconductor channel portion and the insulating cap layer is laterally offset from the interface between the word-line-level semiconductor channel portion and the word-line-level dielectric core.
3. The three-dimensional memory device of claim 2 , wherein a portion of the drain-select-level semiconductor channel portion laterally surrounded by the insulating cap layer has a greater lateral extent than a portion of the drain-select-level semiconductor channel layer laterally surrounded by the word-line-level semiconductor channel portion.
4. The three-dimensional memory device of claim 3 , further comprising a dielectric etch stop material layer overlying the insulating cap layer, wherein a portion of the drain-select-level semiconductor channel portion laterally surrounded by the dielectric etch stop material layer has a lesser lateral extent than the portion of the drain-select-level semiconductor channel portion laterally surrounded by the insulating cap layer.
5. The three-dimensional memory device of claim 3 , wherein the gate dielectric and the cylindrical gate electrode are vertically spaced from the word-line-level semiconductor channel portion by the insulating cap layer and the dielectric etch stop material layer.
6. The three-dimensional memory device of claim 1 , wherein the gate dielectric directly contacts a top surface of the word-line-level semiconductor channel portion.
7. The three-dimensional memory device of claim 6 , wherein:
an interface between the drain-select-level semiconductor channel portion and a bottom portion of the gate dielectric is laterally offset from the interface between the word-line-level semiconductor channel portion and the word-line-level dielectric core; and
a region of the drain-select-level semiconductor channel portion laterally surrounded by the bottom portion of the gate dielectric has a greater lateral extent than a region of the drain-select-level semiconductor channel portion laterally surrounded by the word-line-level semiconductor channel portion.
8. The three-dimensional memory device of claim 7 , further comprising:
an insulating cap layer contacting a topmost one of the insulating layers and laterally surrounding the gate dielectric; and
a dielectric etch stop material layer overlying the insulating cap layer and laterally surrounding the gate dielectric and underlying the cylindrical gate electrode.
9. The three-dimensional memory device of claim 1 , further comprising a dielectric etch stop material layer underlying the cylindrical gate electrode, wherein a region of the drain-select-level dielectric core underlying the dielectric etch stop material layer has a greater lateral extent than a region of the drain-select-level dielectric core that is laterally surrounded by the dielectric etch stop material layer.
10. The three-dimensional memory device of claim 1 , further comprising at least one drain-select-level electrically conductive layer laterally contacting at least a section of a cylindrical outer sidewall of the cylindrical gate electrode.
11. The three-dimensional memory device of claim 10 , further comprising a drain-select-level isolation structure including a concave cylindrical surface that contacts another section of the cylindrical outer sidewall of the cylindrical gate electrode.