Interconnect structure for wafer level package

A package comprising:

• a device die comprising a substrate;
• a molding compound contacting a sidewall of the substrate;
• a metal pad over the substrate;
• a passivation layer comprising a portion covering an edge portion of the metal pad;
• a dielectric layer over the passivation layer, wherein the dielectric layer comprises a portion extending into an opening in the passivation layer, with the portion of the dielectric layer comprises a bottom surface contacting a top surface of the metal pad;
• a first polymer layer over the dielectric layer, wherein the first polymer layer does not extend to directly over the molding compound;
• a second polymer layer over and vertically overlapping the first polymer layer and the molding compound;
• a post-passivation interconnect (PPI) comprising a via extending into an opening that extends into the first and the second polymer layers, wherein the via contacts a top surface of the metal pad, and wherein an edge of the dielectric layer contacts a sidewall of the via;
• and
• a solder ball over the PPI and the second polymer layer, wherein the solder ball is electrically coupled to the metal pad through the PPI.

A method comprising:

• providing a device wafer comprising:
• a device die comprising a substrate;
• a metal pad over the substrate;
• and
• a passivation layer comprising a portion covering an edge portion of the metal pad, wherein a portion of a top surface of the metal pad is not covered by the passivation layer;
• forming a dielectric layer over the device wafer, wherein an entirety of the device wafer is covered by the dielectric layer;
• and
• performing a die saw on the device wafer to separate the device die from additional dies in the device wafer, wherein no patterning is performed to the dielectric layer between the step of blanket forming the dielectric layer and the step of die saw, and wherein the device die comprises the dielectric layer.