Source structure of three-dimensional memory device and method for forming the same
Embodiments of source structure of a three-dimensional (3D) memory device and method for forming the source structure of the 3D memory device are disclosed. In an example, a NAND memory device includes a substrate, an alternating conductor/dielectric stack, a NAND string, a source conductor layer, and a source contact. The alternating conductor/dielectric stack includes a plurality of conductor/dielectric pairs above the substrate. The NAND string extends vertically through the alternating conductor/dielectric stack. The source conductor layer is above the alternating conductor/dielectric stack and is in contact with an end of the NAND string. The source contact includes an end in contact with the source conductor layer. The NAND string is electrically connected to the source contact by the source conductor layer. In some embodiments, the source conductor layer includes one or more conduction regions each including one or more of a metal, a metal alloy, and a metal silicide.
1. A method of forming a NAND memory device, comprising:
forming an alternating conductor/dielectric stack on a first substrate;
forming a NAND string and a source contact both extending vertically through the alternating conductor/dielectric stack; and
replacing the first substrate with a source conductor layer, so that the source conductor layer is in physical contact with a first end of the NAND string and a first end of the source contact, and the NAND string is electrically connected to the source contact by the source conductor layer.
2. The method of claim 1 , wherein replacing the source conductor layer comprises removing the first substrate and disposing one or more of a metal, a metal alloy, and a metal silicide.
3. The method of claim 1 , wherein replacing the first substrate with a source conductor layer comprises:
removing the first substrate; and
forming the source conductor layer at a location occupied by of the first substrate prior to its removal.
4. The method of claim 3 , wherein removing the first substrate comprises:
thinning the first substrate; and
removing the thinned first substrate.
5. The method of claim 1 , wherein replacing the first substrate with a source conductor layer comprises disposing a metal on the first substrate to form a metal silicide layer with the first substrate.
6. The method of claim 5 , wherein forming a metal layer comprises:
thinning the first substrate; and
forming the metal layer on the thinned first substrate.
7. The method of claim 6 , wherein forming a metal layer further comprises:
forming an isolation region at a first surface of the first substrate that is in contact with the alternating conductor/dielectric stack; and
thinning the first substrate from a second surface of the first substrate to expose the isolation region.
8. The method of claim 1 , further comprising forming one or more isolation regions in the source conductor layer.
9. The method of claim 1 , further comprising:
forming a peripheral device on a second substrate; and
joining the first and second substrates so that the NAND string is positioned between the first substrate and the peripheral device.
10. The method of claim 9 , wherein joining the NAND string and the peripheral device comprises:
forming a first interconnect layer in contact with a second end of the NAND string and a second end of the source contact;
forming a second interconnect layer in contact with the peripheral device; and
forming a bonding interface between the first interconnect layer and the second interconnect layer, so that the peripheral device is electrically connected to the NAND string by the first interconnect layer and the second interconnect layer.
11. The method of claim 10 , wherein:
forming the first interconnect layer comprises forming one or more conductor layers in one or more dielectric layers so that the one or more conductor layers are in contact with the second end of the NAND string and the second end of the source contact; and
forming a second interconnect layer comprises forming one or more further conductor layers in one or more further dielectric layers.
12. The method of claim 11 , further comprising forming a bonding interface by one or more of (i) forming chemical bonds between one of the dielectric layers in the first interconnect layer and one of the dielectric layers in the second interconnect layer, and (ii) causing physical inter-diffusion between one of the conductor layers in the first interconnect layer and one of the conductor layers in the second interconnect layer.
13. A method of forming a three-dimensional (3D) memory device, comprising:
forming an alternating conductor/dielectric stack on a first substrate;
forming a plurality of memory strings extending vertically through the alternating conductor/dielectric stack, so that a first end of each of the plurality of memory strings is in contact with a first surface of the first substrate;
removing the first substrate; and
forming a source conductor layer, so that the first end of each of the plurality of memory strings is in physical contact with a first surface of the source conductor layer.
14. The method of claim 13 , further comprising forming a first interconnect layer on a second surface of the source conductor layer.
15. The method of claim 13 , further comprising patterning the source conductor layer to form an isolation region in the source conductor layer.
16. The method of claim 14 , further comprising:
forming a second interconnect layer above the plurality of memory strings on the first substrate;
forming, on a second substrate, a peripheral device;
forming a third interconnect layer above the peripheral device on the second substrate; and
bonding the first substrate and the second substrate, so that the second interconnect layer is above and in contact with the third interconnect layer.