Semiconductor chip suitable for 2.5D and 3D packaging integration and methods of forming the same

An apparatus comprising:

• a first semiconductor chip having a first substrate, a first metal layer, and a plurality of first component portions, wherein:
• the first substrate includes a first substrate base and a plurality of first protrusions at a backside of the first substrate, wherein each of the plurality of first protrusions with a same height protrudes from a bottom surface of the first substrate base, and at least one first via hole extends vertically through one of the plurality of first protrusions and the first substrate base;
• the first metal layer selectively covers exposed surfaces at the backside of the first substrate and fully covers inner surfaces of the at least one first via hole;
• and
• the plurality of first component portions is over a top surface of the first substrate base and a certain one of the plurality of first component portions is electrically coupled to a portion of the first metal layer at a top of the at least one first via hole;
• and
• a second semiconductor chip, which is stacked underneath the first semiconductor chip, having a second substrate and a plurality of second component portions over a top surface of the second substrate, wherein each of the plurality of first protrusions protrudes toward a corresponding second component portion, such that the certain one of the plurality of first component portions is electrically coupled to a certain one of the plurality of second component portions by the first metal layer.