Method of forming package structure

A method comprising:

• attaching a wafer onto a curved surface of a wafer chuck, such that the wafer is warped and physically in contact with the curved surface;
• picking and placing discrete device dies to the wafer, each of the device dies comprising a first dielectric layer, such that the first dielectric layers of the device dies are in contact with a second dielectric layer of the wafer;
• performing an annealing process to bond the first dielectric layers of the device dies to the second dielectric layer;
• encapsulating the device dies with an encapsulating material;
• and
• forming redistribution lines overlapping the encapsulating material and the device dies.

A method comprising:

• providing a wafer chuck comprising a fluid chamber and a flexible material layer over the fluid chamber;
• adjusting a pressure in the fluid chamber to set a profile of a surface of the wafer chuck;
• placing a wafer on the wafer chuck, the wafer being held at the surface of the wafer chuck;
• placing discrete device dies on the wafer;
• directly bonding each of the device dies to the wafer;
• encapsulating each of the device dies with an encapsulating material.