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Abstract

A method of minimizing the volume of the depressions 240 in aluminum cavity filling processes, by-depositing a conformal first layer of aluminum alloy 220 by chemical vapor deposition, long-throw sputtering, collimated sputtering, or ionized physical vapor deposition, to partially fill the cavity 202. This layer is preferably deposited at low temperature (eg. less than 300 degrees C.) and lower deposition pressure (if deposited by sputtering). Subsequently, a second layer of aluminum alloy 230 is deposited by sputtering at temperatures greater than 350 degrees C. and at high power (e.g. greater than 10 kW) to close the mouth of cavity 202. The second layer of aluminum 230 is then forced into the remaining volume of the cavity 202. As part of the cavity 202 is filled with aluminum, alloy 220 before the high pressure aluminum extrusion/reflow, less material is required to be transported into the cavity 202. Therefore, a smaller depression 240 above the cavity is produced. This method is particularly advantageous in multi-level interconnect applications involving aluminum cavity filling.

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