Method of forming vias on a wafer stack using laser ablation

A method of forming a backside connection on a wafer stack, comprising:

• bonding a first wafer to a second wafer to form a wafer stack, each of the first and second wafers including integrated circuitry for a number of die;
• thinning a backside of the first wafer of the stack;
• directing a laser beam at the backside of the first wafer to create a via in the first wafer, the via formed by substantially non-thermal ablation of the first wafer material, wherein one end of the via opens to the backside of the first wafer and an opposing end of the via extends down to a conductive layer in an interconnect structure of the first wafer;
• forming a backside connection at the via, the backside connection including a conductive lead;
• and
• cutting the wafer stack into the number of die, one of the die including the conductive lead.