Effects of the dissolved oxygen in Ti films on Ti reactions in Cu/Ti/SiO2/Si system upon annealing
Authors: Hong, S J; Lee, S; Yang, H J; Lee, H M; Ko, Y K; Hong, H N; Soh, H S; Kim, C K; Yoon, C S; Ban, K S; Lee, J G
Source: Semiconductor Science and Technology, Volume 19, Number 11, November 2004 , pp. 1315-1321(7)
Publisher: IOP Publishing
Abstract:The reactions of Cu/Ti/SiO2 structures at temperatures ranging from 200 to 700 °C have been studied for various Ti thicknesses. X-ray and Rutherford backscattering spectroscopy (RBS) analyses were used to identify the reaction products resulting from Ti reactions in Cu/Ti/SiO2 systems and the oxygen composition in the unreacted Ti, and revealed a correlation between the oxygen concentration in Ti films and the sequences of the Ti reactions. The reaction products initially formed, at around 300 °C, were a series of Cu–Ti intermetallics (Cu3Ti/CuTi) at the Cu–Ti interface with the oxygen dissolved in the Ti moving from the compounds into the remaining unreacted Ti. At 500 °C, the Cu3Ti was converted into Cu-rich intermetallics, Cu4Ti, which grew at the expense of the CuTi due to the increased oxygen content in the Ti. In addition, the outdiffusion of Ti, to the Cu surface, and the Ti–SiO2 reactions caused an abrupt increase in the oxygen content in the Ti layer, which placed thermodynamic restraints on further Ti reactions. Furthermore, thinner Ti layers showed a higher increased rate of oxygen accumulation for the same consumption of Ti, which led to significantly reduced Ti consumption. The diffusion barrier properties of SiO2 for Cu metallization decreased with an increasing Ti thickness.
Document Type: Research Article
Publication date: November 2004