Impact of Rapid Thermal Annealing of Ti/Tin Bilayers On Subsequent Chemical Vapor Deposition Of Tungsten

Abstract

AbstractThe influence of rapid thermal annealing (RTA) of Ti/TiN on the stress in the subsequently deposited tungsten (W) films and on the impurity contents at the TiN-W interface was investigated for two types of Ti/TiN bilayers sputter-deposited at 300 °C and 550 °C. A post treatment of the Ti/TiN bilayers resulted in a substantially decreased stress in the W films. It also led to a considerable reduction of the fluorine contents at the TiN-W interface. Both effects were more pronounced for the W deposited on the low-temperature Ti/TiN bilayers and/or annealed in the NH3 atmosphere, than on the high-temperature Ti/TiN bilayers and/or annealed in the N2 atmosphere. Annealed in N2, the interfacial oxygen at the TiN-W interface increased slightly, which can be attributed to the presence of trace amounts of O2 in the N2 atmosphere. A slight increase in the W film resistivity was thus found for the W films deposited on the N2 annealed Ti/TiN bilayers, while the resistivity decreased somewhat for the W films deposited on the NH3 annealed Ti/TiN bilayers. After the post treatment, a large amount of nitrogen was found incorporated in the Ti layer forming TiNx (× < 0.3). However, the post treatment led to a considerable increase in the tensile stress in the Ti/TiN bilayers, and then an increase in the total stress of the whole Ti/TiN/W system. This stress increase could be controlled by using moderate anneal temperatures (e.g. < 550 °C) for the post treatment.