Chemical removal of oxide layer from chip pads
View Patent ↗Methods are provided for removing an oxide layer from a metal pad on an integrated circuit in order to reduce contact resistance. In one embodiment, aluminum oxide, on the surface of a bond pad substantially comprised of aluminum, is reacted with a first chemical agent to form an inorganic salt, and the inorganic salt is then reacted with a second chemical agent leaving a substantially bare, that is, unoxidized, aluminum surface.
1. A method of preparing wafers for testing, comprising:
providing a wafer having a topside passivation layer formed over an aluminum pad layer, the topside passivation layer having pad openings formed therein;
forming a patterned photoresist layer over the topside passivation layer such that at least portions of the pads are exposed; and
removing a layer of aluminum oxide from the exposed portion of the pads by:
disposing the wafer in a processing chamber and introducing a fluorine-containing gas,
introducing a solvent into the processing chamber, and
exhausting the processing chamber.
2. The method of claim 1 , wherein the aluminum pad layer is disposed over an aluminum bond pad.
3. The method of claim 1 , wherein the fluorine-containing gas is hydrogen fluoride.
4. The method of claim 3 , wherein the solvent comprises a materials selected from the group consisting of water vapor, xylene, and nitric acid.
5. The method of claim 4 , further comprising:
introducing, subsequent to introducing the solvent, an inert gas into the processing chamber.
6. The method of claim 5 , further comprising:
storing the wafer in an oxygen-free environment.
7. The method of claim 6 , wherein the oxygen-free environment is a vacuum or an inert atmosphere.
8. A method of preparing wafers for testing, comprising:
providing a wafer having at least one aluminum pad thereon, and having a topside passivation layer thereon, the topside passivation layer patterned such that at least a first portion of the at least one pad is covered by the topside passivation layer and at least a second portion of the at least one pad is not covered by the topside passivation layer; and
removing a layer of aluminum oxide from the second portion of the at least one pad by:
exposing the wafer to gaseous HF;
exposing the wafer to a solvent;
exposing the wafer to an inert gas; and
maintaining the wafer in an inert gas environment.
9. The method of claim 8 , wherein the solvent is water vapor.
10. The method of claim 8 , wherein the aluminum pad layer is disposed over an aluminum bond pad.