Stress evolution in TiN and TaN layers and multilayers prepared by reactive magnetron sputtering and studied with in-situ laser reflection curvature technique
(English)Manuscript (preprint) (Other academic)
Time-resolved in-situ curvature measurements have been used to measure the stress evolution during UHV-based reactive magnetron sputter deposition of TiN and TaN layers and multilayers at 750° C onto Si wafers. It was fmmd that the stress in the initial TiN layers is compressive and reaches a maximum value of -1.2 GPa at 10 nm, there after the stress evolves to tensile during steady state columnar growth. It is suggested that the initial compressive stress is caused by the affinity of reducing any SiO2 to TixSiyOz and the heat transfer from the discharge to the substrate, corresponding to a temperature raise of ~35 °C on the substrate. The stress evolution in TaN layers gwwn on TiN template layers depends strongly on the nitrogen partial pressure in the discharge, from 1 to 3.5 mTorr. This can be correlated with the condition that TaN undergoes phase transformations as the nitrogen partial pressure increase. At low nitrogen content the dominating phase is the hexagonal γ-Ta2N phase and the stress is as high as -1.0 GPa. At higher nitrogen content the layer is essentially stress free with a mixture of cubic δ-TaN and hexagonal ε-TaNphases. This nitrogen dependence combined with the high time sensitivity of the measuring technique provides means to control the stress or phase composition in a given film during growth. It is also shown that the stress evolution in the individual layers in a TiN/faN superlattice with a period as small as 5 nm can be resolved.
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-85686OAI: oai:DiVA.org:liu-85686DiVA: diva2:572589