Three-dimensional memory device including stairless word line contact structures for and method of making the same

1. A method of forming a semiconductor device, comprising:

forming an alternating stack of insulating layers and sacrificial material layers over a substrate;

forming memory openings through the alternating stack;

forming memory opening fill structures in the memory openings;

forming via cavities vertically extending through the alternating stack without forming any stepped surfaces in the alternating stack;

forming sacrificial via fill structures in the via cavities;

replacing the sacrificial material layers with electrically conductive layers;

forming voids in volumes of the via cavities by removing the sacrificial via fill structures;

forming tubular dielectric spacers on sidewalls of the via cavities; and

forming contact via structures in remaining volumes of the via cavities on an inner sidewall of a respective one of the tubular dielectric spacers and directly on a top surface of a respective one of the electrically conductive layers,

wherein each of the sacrificial material layers contains a respective portion of a top surface that is physically exposed to a respective one of the via cavities upon formation of the via cavities, and

wherein forming the via cavities comprises sequentially performing N sets of via formation processing steps, wherein each i-th set of via formation processing steps comprises:

an i-th etch mask patterning step in which an i-th etch mask layer is formed over the alternating stack and is lithographically patterned to form openings therethrough;

an i-th anisotropic etch step in which at least one pair of an insulating layer and a sacrificial material layer is etched underneath the openings in the i-th etch mask layer; and

an i-th etch mask removal step in which the i-th etch mask layer is removed, wherein N is an integer greater than 1, and i is any integer between 0 and N+1.

2. The method of claim 1 , wherein openings in a j-th etch mask layer includes a respective first subset of openings having an areal overlap with opening in a k-th etch mask layer and a respective second subset of openings that does not have any areal overlap with the openings in the k-th etch mask layer for any pair of j and k that are different from each other and selected from integers in a range between 0 and N+1.

3. The method of claim 1 , wherein:

an anisotropic etch step within the N sets of via formation processing steps etches a single pair of an insulating layer and a sacrificial material layer underneath each opening in a respective etch mask layer;

another anisotropic etch step within the N sets of via formation processing steps etches two pairs of an insulating layer and a sacrificial material layer underneath each opening in a respective etch mask layer; and

yet another anisotropic etch step within the N sets of via formation processing steps etches four pairs of an insulating layer and a sacrificial material layer underneath each opening in a respective etch mask layer.

4. The method of claim 1 , wherein:

the integer N is in a range from 4 to 8; and

a total number of sacrificial material layers that are physically exposed to the via cavities after the N sets of via formation processing steps is in a range from 2 N-1 to 2 N −1.

5. A method of forming a semiconductor device, comprising:

forming an alternating stack of insulating layers and sacrificial material layers over a substrate;

forming memory openings through the alternating stack;

forming memory opening fill structures in the memory openings;

forming via cavities vertically extending through the alternating stack without forming any stepped surfaces in the alternating stack;

forming sacrificial via fill structures in the via cavities;

replacing the sacrificial material layers with electrically conductive layers;

forming voids in volumes of the via cavities by removing the sacrificial via fill structures;

forming tubular dielectric spacers on sidewalls of the via cavities; and

forming contact via structures in remaining volumes of the via cavities on an inner sidewall of a respective one of the tubular dielectric spacers and directly on a top surface of a respective one of the electrically conductive layers,

wherein the sacrificial via fill structures are formed by:

depositing a sacrificial fill material in the via cavities; and

removing portions of the sacrificial fill material from above the alternating stack.

6. A method of forming a semiconductor device, comprising:

forming an alternating stack of insulating layers and sacrificial material layers over a substrate;

forming memory openings through the alternating stack;

forming memory opening fill structures in the memory openings;

forming via cavities vertically extending through the alternating stack without forming any stepped surfaces in the alternating stack;

forming sacrificial via fill structures in the via cavities;

replacing the sacrificial material layers with electrically conductive layers;

forming voids in volumes of the via cavities by removing the sacrificial via fill structures;

forming tubular dielectric spacers on sidewalls of the via cavities; and

forming contact via structures in remaining volumes of the via cavities on an inner sidewall of a respective one of the tubular dielectric spacers and directly on a top surface of a respective one of the electrically conductive layers,

wherein replacing the sacrificial material layers with the electrically conductive layers comprises:

forming a backside trench vertically extending through each layer within the alternating stack;

forming backside recesses selective to the insulating layers and the sacrificial via fill structures;

depositing a backside blocking dielectric layer in each of the backside recesses and on bottom surfaces of the sacrificial via fill structures; and

depositing at least one electrically conductive material in the backside recesses, wherein the electrically conductive layers are formed in remaining volumes of the backside recesses after depositing the backside blocking dielectric layer.

7. The method of claim 6 , further comprising removing portions of the backside blocking dielectric layer after removal of the sacrificial via fill structures, wherein each of the contact via structures is formed directly on a respective sidewall of the backside blocking dielectric layer.

8. The method of claim 6 , wherein:

cylindrical surfaces of the backside blocking dielectric layer are physically exposed to the voids in the volumes of the via cavities by removing the sacrificial via fill structures; and

the contact via structures are formed directly on the cylindrical surfaces of the backside blocking dielectric layers.

9. A method of forming a semiconductor device, comprising:

forming an alternating stack of insulating layers and sacrificial material layers over a substrate;

forming memory openings through the alternating stack;

forming memory opening fill structures in the memory openings;

forming via cavities vertically extending through the alternating stack without forming any stepped surfaces in the alternating stack;

forming sacrificial via fill structures in the via cavities;

replacing the sacrificial material layers with electrically conductive layers;

forming voids in volumes of the via cavities by removing the sacrificial via fill structures;

forming tubular dielectric spacers on sidewalls of the via cavities; and

forming contact via structures in remaining volumes of the via cavities on an inner sidewall of a respective one of the tubular dielectric spacers and directly on a top surface of a respective one of the electrically conductive layers,

wherein:

the memory openings are formed in a memory array region;

the via cavities are formed in a contact region that is adjacent to the memory array region; and

each of the memory opening fill structures comprises a vertical semiconductor channel and a memory film, and

the method further comprising:

forming support openings through the alternating stack in the contact region concurrently with formation of the memory openings; and

forming support pillar structures in the support openings concurrently with formation of the memory opening fill structures.

10. A method of forming a semiconductor device, comprising:

forming an alternating stack of insulating layers and sacrificial material layers over a substrate;

forming memory openings through the alternating stack;

forming memory opening fill structures in the memory openings;

forming via cavities vertically extending through the alternating stack without forming any stepped surfaces in the alternating stack;

forming sacrificial via fill structures in the via cavities;

replacing the sacrificial material layers with electrically conductive layers;

forming voids in volumes of the via cavities by removing the sacrificial via fill structures;

forming tubular dielectric spacers on sidewalls of the via cavities; and

forming contact via structures in remaining volumes of the via cavities on an inner sidewall of a respective one of the tubular dielectric spacers and directly on a top surface of a respective one of the electrically conductive layers,

wherein:

the memory openings are formed in a memory array region;

support pillar structures and the via cavities are formed in a contact region that is adjacent to the memory array region;

each of the memory opening fill structures comprises a vertical semiconductor channel and a memory film; and

the via cavities and the support pillar structures are formed in respective areas such that areas of the via cavities do not overlap with areas of the support pillar structures.