Die stacking structure and method forming same

A structure comprising:

• a package comprising:
• a device die comprising:
• a semiconductor substrate;
• a probe pad;
• and
• a solder region over and contacting the probe pad;
• a package component over and bonding to the device die;
• a first molding compound molding the package component therein, wherein all sidewalls and an entire top surface of the solder region are in direct contact with the first molding compound;
• a dielectric layer underlying the device die, wherein edges of the dielectric layer are flush with corresponding edges of the first molding compound and the device die;
• and
• non-solder conductive features underlying the semiconductor substrate of the device die, wherein the non-solder conductive features extend into the dielectric layer;
• and
• a plurality of redistribution lines underlying and physically contacting the non-solder conductive features, wherein the plurality of redistribution lines are distributed in an area laterally extending beyond corresponding first edges of the package.

A structure comprising:

• a first device die comprising:
• a semiconductor substrate;
• a first plurality of electrical connectors over the semiconductor substrate;
• and
• a second plurality of electrical connectors over the semiconductor substrate, wherein both of a first one and a second one of the second plurality of electrical connectors comprises:
• a metal pillar;
• and
• a solder region over the metal pillar;
• a second device die over and bonding to the first device die through the first plurality of electrical connectors;
• and
• a first molding compound molding the second device die and the second plurality of electrical connectors therein, wherein the second plurality of electrical connectors are overlapped by, and are in physical contact with, the first molding compound molding, wherein an entire top surface of the solder region is in contact with the first molding compound.