Contact structures for three-dimensional memory
Embodiments of 3D memory structures and methods for forming the same are disclosed. The fabrication method includes disposing an alternating dielectric stack on a substrate, wherein the alternating dielectric stack having first and second dielectric layers alternatingly stacked on top of each other. Next, a plurality of contact openings can be formed in the alternating dielectric stack such that a dielectric layer pair can be exposed inside at least one of the plurality of contact openings. The method further includes forming a film stack of alternating conductive and dielectric layers by replacing the second dielectric layer with a conductive layer, and forming a contact structure to contact the conductive layer in the film stack of alternating conductive and dielectric layers.
1. A three-dimensional (3D) memory structure, comprising:
a film stack comprising conductive and dielectric layers alternatingly stacked on top of each other in a first direction;
a common source contact penetrating the film stack in the first direction;
memory strings in a channel structure region penetrating through the film stack in the first direction, wherein each of the memory strings comprises a memory film and a channel layer;
contact structures in the channel structure region penetrating through one or more of the conductive and dielectric layers in the first direction such that a respective conductive layer of the film stack is electrically connected to at least one of the contact structures; and
dummy memory strings adjacent to the contact structures and penetrating through the film stack in the first direction, each of the dummy memory strings comprising a core filling film, wherein:
each of the contact structures comprises a liner surrounding a conductive material;
the conductive material contacts the respective conductive layer of the film stack;
the liner comprises an insulator configured to electrically isolate the contact structures from one or more conductive layers of the film stack in a second direction perpendicular to the first direction and is distant from the respective conductive layer of the film stack in the first direction;
at least one memory string is directly adjacent to two contact structures that are on opposite sides of the at least one memory string in the second direction; and
the common source contact comprises an isolation liner configured to electrically isolate the common source contact from the conductive layers of the film stack.
2. The 3D memory structure of claim 1 , wherein the contact structures are coplanar with the film stack.
3. The 3D memory structure of claim 1 , wherein the contact structures are randomly distributed in the channel structure region.
4. The 3D memory structure of claim 1 , wherein each of the contact structures is directly adjacent to at least two memory strings.
5. The 3D memory structure of claim 1 , further comprising:
two directly adjacent contact structures electrically connected to a first conductive layer and a second conductive layer of the film stack, respectively, wherein one or more conductive layers of the film stack are located between the first conductive layer and the second conductive layer.