Three-dimensional memory devices having through array contacts and methods for forming the same

A method for forming a three-dimensional (3D) memory device, comprising:

• forming a lower stack comprising interleaved a plurality of dielectric layers and a plurality of sacrificial layers above a substrate;
• forming a lower channel structure extending vertically through the lower stack;
• forming an upper stack comprising interleaved a plurality of dielectric layers and a plurality of sacrificial layers above the lower stack;
• forming an upper channel structure extending vertically through the upper stack and connecting to the lower channel structure;
• forming an opening through the lower stack and the upper stack;
• forming a spacer in a plurality of shallow recesses and on a sidewall of the opening, wherein the plurality of shallow recesses abut the sidewall of the opening;
• depositing a conductor layer in the opening to form a through array contact (TAC);
• and
• forming a slit extending vertically through the stack.

A method for forming a three-dimensional (3D) memory device, comprising:

• forming a stack comprising interleaved a plurality of dielectric layers and a plurality of sacrificial layers above a substrate;
• forming a channel structure extending vertically through the stack;
• etching a first opening through the stack, a second opening outside of the stack, and a third opening through the stack
• depositing a dielectric layer (i) in the third opening to form a dummy channel structure and (ii) in the first opening and the second opening;
• removing parts of the dielectric layer that are deposited on a bottom surface of the first opening and on a bottom surface of the second opening;
• depositing a conductor layer (i) in the first opening to form a through array contact (TAC) and (ii) in the second opening to form a peripheral contact;
• and
• forming a slit extending vertically through the stack.