A method includes bonding a first semiconductor die and a second semiconductor die to a substrate, where a gap is disposed between a first sidewall of the first semiconductor die and a second sidewall of the second semiconductor die, performing a plasma treatment to dope top surfaces and sidewalls of each of the first semiconductor die and the second semiconductor die with a first dopant, where a concentration of the first dopant in the first sidewall decreases in a vertical direction from a top surface of the first semiconductor die towards a bottom surface of the first semiconductor die, and a concentration of the first dopant in the second sidewall decreases in a vertical direction from a top surface of the second semiconductor die towards a bottom surface of the second semiconductor die, and filling the gap with a spin-on dielectric material.

A wafer includes a substrate and conductive bumps on a surface of the substrate. In a plan view from a direction perpendicular to the surface of the substrate, the area density of the conductive bumps is higher in a first area than in a second area around the first area in the surface of the substrate. The first area has effective chip areas arranged therein.

A composite package may have a feature for enhancing thermal dissipation. The feature may include an array of metal pillar located on a backside a semiconductor die. Alternatively, the feature may include a cavity, to which a backside surface of a semiconductor die is exposed and which is laterally surrounded by a portion of a molding compound die frame.