Buffer Design for Package Integration

A method comprising:

• forming a first package comprising:
• bonding a first device die and a second device die to an interposer die;
• encapsulating the first device die and the second device die in inorganic gap-fill materials;
• forming through-vias on metal pads of the interposer die, wherein the through-vias penetrate through the inorganic gap-fill materials, and are electrically connect to the first device die and the second device die through the interposer die;
• forming a dielectric layer over the first device die, the second device die, and the through-vias;
• forming metal features in the dielectric layer, wherein the metal features are formed using a damascene process;
• forming a polymer layer over the metal features, wherein all dielectric materials underlying the polymer layer are inorganic materials;
• and
• forming an electrical connector over the polymer layer;
• and
• bonding the first package to a second package, wherein the electrical connector is bonded to the second package.

A method comprising:

• forming a first package comprising:
• forming a first interconnect structure, wherein the first interconnect structure is free from polymers therein;
• bonding a device die over the first interconnect structure;
• disposing a dielectric region, with the device die being in the dielectric region;
• and
• forming a second interconnect structure over the device die and the dielectric region, wherein the second interconnect structure comprises a polymer layer;
• and
• bonding a second package to the first package through solder region.