Ultrathin microelectronic die packages and methods of fabricating the same

A method of fabricating an ultrathin microelectronic package, comprising:

• forming a microelectronic substrate having a first surface;
• attaching a plurality of microelectronic dice to the microelectronic substrate, wherein each microelectronic die of the plurality of microelectronic dice include interconnects extending from a first surface of each of the plurality of the microelectronic die to the microelectronic substrate first surface;
• depositing an underfill material between each microelectronic die of the plurality of microelectronic dice and the microelectronic substrate, and around the interconnects;
• and
• introducing an etchant to a back surface of each microelectronic die of the plurality of microelectronic dice to remove a portion thereof.

A method of fabricating an ultrathin microelectronic package, comprising:

• forming a microelectronic substrate having a first surface;
• attaching a plurality of microelectronic dice to the microelectronic substrate, wherein each microelectronic die of the plurality of microelectronic dice include interconnects extending from a first surface of each of the plurality of the microelectronic die to the microelectronic substrate first surface;
• depositing an underfill material between each microelectronic die of the plurality of microelectronic dice and the microelectronic substrate, and around the interconnects;
• placing an etch blocking structure on exposed areas of the microelectronic substrate first surface prior to etching the microelectronic die;
• introducing an etchant to a back surface of each microelectronic die of the plurality of microelectronic dice to remove a portion thereof;
• and
• removing a fillet portion of the underfill material.