Cobalt Metallurgy for Vlsi
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2005-Mar-09
This article relates generally to fabrication of integrated circuits and, more particularly, to the sequence of metal layers used during fabrication. An adhesion layer of cobalt between tungsten and copper layers eliminates undercutting of the copper during etching of the tungsten. Since copper does not adhere well to tungsten, an intermediate adhesion layer is required; cobalt is an excellent adhesion layer and etch stop since it does not erode during dry etching processes. Cobalt followed by copper can be deposited onto tungsten in successive steps by means of a lift-off mask. After the mask is removed, the exposed tungsten under the mask can be dry-etched without damage to either the etch- resistant cobalt or copper. This cobalt-copper combination is stable to a temperature of a least 600ŒC.