Study of adhesion and chemical bonds in the reaction layer formed at Cu-Mn interconnection/SiO2 interface

Abstract

In this study, adhesion of the Cu/Cu-Mn stacked interconnections to glass (SiO2) substrates was evaluated and the results were correlated with a detailed analysis of the reaction layer between the Cu-Mn and the chemical vapour deposited SiO2. When the Mn concentrations were varied, an abrupt change in the adhesion properties was observed; the practical adhesion properties were obtained in the Cu/Cu-Mn interconnections with Mn concentrations at 8% and higher. To clarify the chemical nature and the microstructure of the reaction layer at the interface between the Cu-x Mn (x = 4, 10 at. %) and the SiO2 layers was analysed using angle-resolved x-ray photoelectron spectroscopy and transmission electron microscope-electron energy loss spectroscopy. These observations indicated that the cross-sectional structure along the reaction layer of the Cu–10 at. % Mn sample can be divided into two regions: in the high Mn region, the Mn-Si complex oxide and the SiO2 mixture phase are preferable due to a decrease in the oxygen fraction near the Cu-Mn layer, whereas in the low Mn region, MnOx and SiO2 mixture are stable. The Mn-Si complex oxide was observed only in the high adhesive sample (Mn 10 at. %). These results suggest that the existence of the chemical bond of the Mn-Si complex oxide improved the interfacial adhesion between the Cu/Cu-Mn stacked interconnections and the glass substrates.

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. − …”