Passivation scheme

A method, comprising:

• forming a first passivation layer over an electrically conductive pad, wherein the electrically conductive pad comprises copper or copper alloy and the passivation layer has a thickness that ranges from 500 Å to 1500 Å;
• forming a second passivation layer over the first passivation layer;
• forming a first opening through the second passivation layer over the electrically conductive pad, wherein the first opening does not reach the electrically conductive pad;
• forming a stress buffer layer comprising polymer over the second passivation layer and the first opening, wherein a bottom surface of the stress buffer layer directly adjoins the first passivation layer;
• forming a second opening through the stress buffer layer over the electrically conductive pad wherein the second opening does not reach the electrically conductive pad;
• curing the stress buffer layer;
• and
• extending the second opening through the first passivation layer to reach the electrically conductive pad by self-aligned etching using the stress buffer layer as a mask after the curing.

A method comprising:

• forming a conductive pad over a first surface of a substrate;
• forming a first passivation layer over the first surface of the substrate;
• forming a second passivation layer over the first passivation layer;
• forming a first opening through the second passivation layer to the first passivation layer;
• forming a first stress buffer layer over the second passivation layer and in the first opening;
• forming a second opening through the first stress buffer layer to the first passivation layer, a first portion of the first buffer layer being between a sidewall of the first opening and a sidewall of the second opening;
• performing a treatment on the first stress buffer layer;
• and
• after performing the treatment on the first stress buffer layer, extending the second opening through the first passivation layer to expose a portion of the conductive pad.