Three-dimensional (3D) integrated circuit (IC) (3DIC) package employing a redistribution layer (RDL) interposer facilitating semiconductor die stacking, and related fabrication methods

An integrated circuit (IC) package, comprising:

• an interposer, comprising:
• a first surface and a second surface opposing the first surface;
• and
• one or more redistribution layers (RDLs) between the first surface and the second surface, the one or more RDLs comprising:
• a first RDL comprising:
• a first metal interconnect;
• and
• a second metal interconnect;
• a first die disposed in the interposer, the first die comprising a first die interconnect embedded in the first die and coupled to the first metal interconnect;
• and
• a second die coupled to the first surface of the interposer, the second die comprising a second die interconnect embedded in the second die, wherein the first die interconnect of the first die is directly bonded to the second die interconnect of the second die, coupling the second die interconnect to the first metal interconnect, the second die further comprising:
• an outer die interconnect embedded in the second die and coupled to the second metal interconnect, the second metal interconnect coupled to a region of the first RDL laterally offset from a footprint of the second die on the first surface of the interposer.