Die stack structure and manufacturing method thereof

A die stack structure, comprising:

• a first die;
• an encapsulant laterally encapsulating the first die;
• a redistribution layer, disposed below the encapsulant and electrically connected with the first die;
• a second die, disposed between the redistribution layer and the first die, wherein the first and second dies are electrically connected with each other,
• wherein the second die comprises a body portion having a first side surface, a second side surface and a third side surface, the second side surface located between the first and third side surfaces connects the first side surface and the third side surface, a first obtuse angle is included between the first side surface and the second side surface, and a second obtuse angle is included between the second side surface and the third side surface, and the second die comprises a flange portion surrounding the body portion, wherein the flange portion has an outer profile vertically aligned with an outer profile of the encapsulant.

A method of manufacturing a die stack structure, comprising:

• providing a semiconductor wafer having first dies;
• performing a trench forming process on the first dies of the semiconductor wafer, the trench forming process comprising:
• providing a mask with openings;
• and
• performing an anisotropic etching with the mask to form ring-shaped trenches in the first dies of the semiconductor wafer corresponding to the openings, wherein each of the first dies of the semiconductor wafer comprises a flange portion located right under the corresponding ring-shaped trench and a body portion laterally surrounded by the corresponding ring-shaped trench and the flange portion;
• bonding seconds dies onto the first dies of the semiconductor wafer;
• encapsulating the second dies by an encapsulant to form a molded wafer;
• forming a redistribution layer on the molded wafer;
• and
• performing a singulation process to the molded wafer, wherein the flange portion has an outer profile vertically aligned with an outer profile of the encapsulant.