Reliable plasma dicing of wafers to singulate it into individual dies is disclosed. Laser processing is employed to form mask openings in a passivation stack of a processed wafer. The patterned passivation stack serves as a plasma dicing mask for plasma dicing the wafer. The sidewalls of the mask openings may be flat or vertical sidewalls. In other cases, the sidewalls of the mask openings are slanted or chamfered sidewalls. The plasma dices the wafer using first and second plasma etch steps. The first plasma etch step etches to form scalloped sidewalls on the first portion of the die and the second plasma step etches to form flat or vertical sidewalls on a second portion of the die. The second portion of the die is the lower portion of the substrate or wafer. This prevents backside notching to improve reliability.