Patent ID: 7993971

Claim:
A method for forming semiconductor structure, comprising: forming a first contact pad on a first die, wherein the first contact pad comprises a first metal element; forming a metal over the first contact pad, wherein the metal comprises a second metal element, and the second metal element is different from the first metal element; forming a barrier layer on the first die, wherein a first portion of the barrier layer is under the first contact pad and a second portion of the barrier layer is adjacent the first contact pad; removing the second portion of the barrier layer; forming an oxide of the first metal element on sidewalls of the first contact pad after removing the second portion of the barrier layer; rapidly reflowing a portion of the metal to form a thin intermetallic layer, wherein the thin intermetallic layer is formed as a result of an interaction between the first metal element and the second metal element; and attaching the first contact pad of the first die to a second contact pad of a second die, wherein attaching comprises heating the first contact pad and the second contact pad to reflow the metal to form an intermetallic layer such that substantially all of the metal formed over the first contact pad is used as part of the intermetallic layer, wherein the intermetallic layer is formed as a result of an interaction between the first metal element, the second metal element, and at least a portion of the thin intermetallic layer.