In the manufacture of semiconductor wafers and integrated circuits, interconnects, such as vias and trenches, are formed by various techniques, including single and dual damascene processes. Additionally, metal films are deposited on semiconductor substrates, oxides and other dielectrics. Sometimes metal films are used for forming interconnect lines, metallic contacts, conductive vias, metallic interconnects and other conductive features on and above various surfaces of the semiconductor wafers. Typically, the films can be chemically mechanically polished to form the desired interconnect posts and interconnect structures formed from via/trenches.
Typically, aluminum has been a preferred conductive metal because it avoids various problems, such as a high contact resistance with silicon, which normally accompanies the use of gold and copper. Copper also suffers drawbacks compared to aluminum because copper migrates in the device areas, causing problems in device performance. Aluminum, on the other hand, has good adhesion to silicon dioxide and performs well with plasma etching, as compared to copper, which does not perform adequately with plasma etching processes.
Recently, greater interest has been shown by manufacturers of semiconductor devices and the use of copper and copper alloys for metallization patterns, such as in conductive vias and patterns (e.g., trench structures). Copper has a lower resistivity than aluminum. Unfortunately, the standard processes used for pattern definition with semiconductors have not been adequately used with copper integrated circuit metallization, and especially with copper interconnects. These processes include conventional dry etched techniques and selective deposition techniques. However, chemical mechanical polishing (CMP) techniques have been found useful in patterning copper layers. Even with the more efficient chemical mechanical polishing techniques, it is still necessary to passivate copper interconnects such as in via/trench structures, and such as copper plugs used in copper interconnects. Copper has the tendency to corrode, and thus, passivation is necessary.