In some embodiments, an adhesive layer (not shown) is deposited or laminated over the carrier 101 before the dielectric layer 110 is formed. The adhesive layer may be photosensitive and may be easily detached from the carrier 101 by, e.g., shining an ultra-violet (UV) light on the carrier 101 in a subsequent carrier de-bonding process. For example, the adhesive layer may be a light-to-heat-conversion (LTHC) coating made by 3M Company of St. Paul, Minn. or other suppliers.

Still referring to FIG. 1, conductive pillars 119 are formed over the dielectric layer 110. The conductive pillars 119 may be formed by: forming a seed layer over the dielectric layer 110; forming a patterned photoresist over the seed layer, where each of the openings in the patterned photoresist corresponds to a location of the conductive pillar 119 to be formed; filling the openings with an electrically conductive material such as copper using, e.g., electroplating or electroless plating; removing the photoresist using, e.g., an ashing or a stripping process; and removing portions of the seed layer on which the conductive pillars 119 are not formed. Other methods for forming the conductive pillars 119 are also possible and are fully intended to be included within the scope of the present disclosure. In some embodiments, the dielectric layer 110 is omitted, and the conductive pillars 119 are formed on the adhesive layer (e.g., LTHC coating) deposited or laminated over the carrier 101.