Self-forming Al oxide barrier for nanoscale Cu interconnects created by hybrid atomic layer deposition of Cu–Al alloy

Abstract

The authors synthesized a Cu–Al alloy by employing alternating atomic layer deposition (ALD) surface reactions using Cu and Al precursors, respectively. By alternating between these two ALD surface chemistries, the authors fabricated ALD Cu–Al alloy. Cu was deposited using bis(1-dimethylamino-2-methyl-2-butoxy) copper as a precursor and H2 plasma, while Al was deposited using trimethylaluminum as the precursor and H2 plasma. The Al atomic percent in the Cu–Al alloy films varied from 0 to 15.6 at. %. Transmission electron microscopy revealed that a uniform Al-based interlayer self-formed at the interface after annealing. To evaluate the barrier properties of the Al-based interlayer and adhesion between the Cu–Al alloy film and SiO2 dielectric, thermal stability and peel-off adhesion tests were performed, respectively. The Al-based interlayer showed similar thermal stability and adhesion to the reference Mn-based interlayer. Our results indicate that Cu–Al alloys formed by alternating ALD are suitable seed layer materials for Cu interconnects.

Evidence of Mixed Oxide Formation on the Cu/SiO2 Interface

“…However, Cu diffuses rapidly in Si and SiO 2 , which causes degradation of electronic devices at relatively low temperature. During the last decades, a great effort has been done not only to find a suitable interdiffusion barrier material but also for the development of fabrication processes. − Several groups are studying self-forming barriers, fabricated by direct deposition of Cu–metal alloys or partially oxidized manganese onto the SiO 2 which form silicates that act as an effective Cu diffusion barrier. − …”

Atomic layer deposition of transition metal films and nanostructures for electronic and catalytic applications

“…73 The deposition of Cu-Al alloy has also been demonstrated by alternate deposition from Cu and Al precursors at 150 o C (Table 1, entry 41). 86 Cu was deposited from bis…”

“…ALD of CuMg and CuAl alloys were proposed, where the ALD films were subjected to heat treatment, to promote the diffusion of Mg and Al ions to the interface, thus acting as the barrier layer between the Cu and the substrate. 82,86 Potential future applications include the development of nanostructured Ni-Fe permalloys, used as magnetic core in electronic and electrical equipment. 83…”

Intermediate Cu-O-Si Phase in the Cu-SiO2/Si(111) System: Growth, Elemental, and Electrical Studies

“…The study of metal, silicon (Si) interactions, − and formation of interface is important owing to its application in the electronics and semiconductor industry. − With Si-based technologies still governing the integrated circuits, the Cu–Si system has been of particular importance in delivering promising applications from silicon bronzes to catalysis, − microelectronics, Li-ion batteries, , solar cells, − and more. Copper (Cu) with its low cost, low electrical resistivity (∼1.7 μΩ cm), high melting point (1357.6 K), and low diffusivity showed tremendous potential over aluminum for applications in the electronic devices such as Schottky junctions, metal gates and local interconnects …”