Package structure with buffer layer embedded in lid layer

A package structure, comprising:

• a package substrate;
• a first die, disposed on the package substrate and having a first sidewall and a second sidewall opposite to each other;
• a stiffener ring, disposed on the package substrate to laterally surround the first die, wherein the stiffener ring has an inner sidewall facing the first die, the inner sidewall at least has a slant sidewall facing the first sidewall of the first die, and the first sidewall and the slant sidewall enclose a space;
• and
• a lid layer, disposed on the stiffener ring and overlying the first die, wherein the lid layer has an opening penetrating through a top surface of the lid layer and a bottom surface of the lid layer, and the opening corresponds and exposes the space enclosed by the first sidewall of the first die and the slant sidewall of the stiffener ring.

A method of forming a package structure, comprising:

• forming a first die on a package substrate, wherein the first die has a first sidewall and a second sidewall opposite to each other;
• forming a plurality of second dies side by side on the package substrate, wherein the first die is formed between the plurality of second dies;
• forming a stiffener ring on the package substrate to surround the first die and the plurality of second dies, wherein a first sidewall of the first die is close to a first side of the stiffener ring, and encloses a space with the first side of the stiffener ring;
• forming a lid layer on the stiffener ring to overlay the first die and the plurality of second dies;
• and
• forming an opening to penetrate through a top surface and a bottom surface of the lid layer, wherein the opening corresponds and exposes the space enclosed by the first sidewall of the first die and the first side of the stiffener ring.