Effect of deposition temperature on thermal stabilities of copper-carbon films in barrier-less Cu metallization

摘要

Copper-carbon alloy films have been applied in barrier-less Cu metallization as seed layers for improving the thermal stabilities. The effect of the deposition temperature on the microstructure and properties of C-doped Cu films on Si substrates was investigated. The films were prepared by ion beam-assisted deposition at various deposition temperatures by co-sputtering of Cu and graphite targets. No inter-diffusion between Cu and Si was observed in Cu(C) films throughout this experiment, because XRD patterns corresponding to their deep-level reaction product, namely, Cu3Si, were not observed in XRD patterns and EDS results of Cu(C) films. Amorphous carbon layer and SiC layer were found in the interface of Cu(C) as-deposited films when deposition temperature rose to 100 degrees C by TEM, high-resolution image and Fourier transformation pattern. The Cu(C) films deposited at 100 degrees C had the best thermal stabilities and the lowest electrical resistivity of 4.44 mu W cm after annealing at 400 degrees C for 1 h. Cu agglomeration was observed in Cu(C) alloy films with deposition temperatures of 200, 300 and 400 degrees C, and the most serious agglomeration occurred in Cu(C) films deposited at 200 degrees C. Undesired Cu agglomeration resulted in a sharp increase in the resistivity after annealing at 300 degrees C for 1 h. The deposition temperature of 100 degrees C reflected the superior thermal stabilities of Cu(C) seed layers compared with those of other layers. (C) 2017 Elsevier B.V. All rights reserved.