Local contacts of three-dimensional memory devices and methods for forming the same

Abstract

Embodiments of 3D memory devices and methods for forming the same are disclosed. In an example, a 3D memory device includes: a memory stack comprising interleaved conductive layers and dielectric layers; a plurality of channel structures extending vertically through the memory stack; a plurality of channel local contacts each located above and in contact with a corresponding one of the plurality of channel structures, and having a metal material; and a slit structure extending vertically through the memory stack and laterally along a first direction to separate the plurality of channel structures. The slit structure comprises a contact. The contact comprises a first contact portion having a semiconductor material and a second contact portion above the first contact portion and having the metal material. An upper end of the second contact portion and upper ends of the plurality of channel local contacts are coplanar.

What is claimed is: 
     
         1 . A three-dimensional (3D) memory device, comprising:
 a memory stack comprising interleaved conductive layers and dielectric layers;   a plurality of channel structures extending vertically through the memory stack;   a plurality of channel local contacts each located above and in contact with a corresponding one of the plurality of channel structures, and having a metal material; and   a slit structure extending vertically through the memory stack and laterally along a first direction to separate the plurality of channel structures, wherein the slit structure comprises a contact, the contact comprising:
 a first contact portion having a semiconductor material; and 
 a second contact portion above the first contact portion and having the metal material, wherein an upper end of the second contact portion and upper ends of the plurality of channel local contacts are coplanar. 
   
     
     
         2 . The 3D memory device of  claim 1 , wherein:
 the slit structure comprises a spacer laterally between the contact of the slit structure and the conductive layers of the memory stack.   
     
     
         3 . The 3D memory device of  claim 2 , wherein:
 the upper end of the second contact portion of the slit structure does not exceed an upper end of the spacer;   a lower end of the first contact portion of the slit structure exceeds a lower end of the spacer.   
     
     
         4 . The 3D memory device of  claim 3 , wherein:
 a thickness of the upper end of the spacer in a second direction perpendicular to the first direction is less than a thickness of the lower end of the spacer in the second direction.   
     
     
         5 . The 3D memory device of  claim 4 , wherein a width of the upper end of the second contact portion in the second direction is not greater than a distance between outer sidewalls of the spacer. 
     
     
         6 . The 3D memory device of  claim 5 , wherein the width of the upper end of the second contact portion in the second direction is greater than a diameter of each of the plurality of channel local contacts. 
     
     
         7 . The 3D memory device of  claim 5 , wherein the width of the upper end of the second contact portion in the second direction is greater than a maximum width of the first contact portion in the second direction. 
     
     
         8 . The 3D memory device of  claim 1 , wherein each channel structure of the plurality of channel structures comprises a semiconductor channel, a memory film, and a channel plug in a top portion of the channel structure and in contact with a corresponding one of the plurality of channel local contacts. 
     
     
         9 . The 3D memory device of  claim 1 , wherein:
 the plurality of channel structures function as NAND memory strings.   
     
     
         10 . The 3D memory device of  claim 1 , wherein:
 the semiconductor material comprises polysilicon; and   the metal material comprises tungsten.   
     
     
         11 . A three-dimensional (3D) memory device, comprising:
 a memory stack comprising interleaved conductive layers and dielectric layers;   a slit extending vertically through the memory stack and laterally extending in a first direction;   two spacer layers on two sidewalls of the slit, respectively; and   a contact sandwiched between the two spacer layers, and comprising:
 a first contact portion having a lower end exceeds lower ends of the two spacer layers, and 
 a second contact portion having an upper end does not exceed upper ends of the two spacer layers 
   
     
     
         12 . The 3D memory device of  claim 11 , further comprising:
 a plurality of channel structures extending vertically through the memory stack; and   a plurality of channel local contacts each located above and in contact with a corresponding one of the plurality of channel structures.   
     
     
         13 . The 3D memory device of  claim 12 , wherein the slit laterally extending along a first direction to separate the plurality of channel structures. 
     
     
         14 . The 3D memory device of  claim 12 , wherein:
 the first contact portion comprises a first material; and   the second contact portion and the plurality of channel local contacts comprises a second material different from the first material.   
     
     
         15 . The 3D memory device of  claim 14 , wherein:
 the first material comprises semiconductor; and   the second material comprises metal.   
     
     
         16 . The 3D memory device of  claim 14 , wherein:
 the first material comprises polysilicon; and   the second material comprises tungsten.   
     
     
         17 . The 3D memory device of  claim 12 , wherein:
 the upper end of the second contact portion and upper ends of the plurality of channel local contacts are coplanar.   
     
     
         18 . The 3D memory device of  claim 11 , wherein a width of the upper end of the second contact portion in a second direction perpendicular to the first direction is not greater than a distance between outer sidewalls of the spacer. 
     
     
         19 . The 3D memory device of  claim 18 , wherein the width of the upper end of the second contact portion in the second direction is greater than a diameter of each of the plurality of channel local contacts. 
     
     
         20 . The 3D memory device of  claim 11 , wherein each channel structure of the plurality of channel structures comprises a semiconductor channel, a memory film, and a channel plug in a top portion of the channel structure and in contact with a corresponding one of the plurality of channel local contacts.