Reduction in resistivity of 50 nm wide Cu wire by high heating rate and short time annealing utilizing misorientation energy

Abstract

The resistivities and microstructures for 50 nm Cu wires fabricated by high heating rate (3 K/s) and short time (1 min) annealing using infrared rapid thermal annealing equipment have been investigated as a function of annealing temperature and compared to those properties for wires fabricated by a slow heating rate (0.08 K/s), long time (30 min) conventional H2 annealing process. The resistivity of wires annealed by the new process decreased substantially with increasing annealing temperature from 573 to 773 K. The resistivity had its lowest value between 773 and 873 K, and it increased rapidly with annealing temperature above 923 K. The average ρ value was 2.98 μΩ cm for 773 K new process wires, whereas average ρ values were about 3.55 μΩ cm for 573 K and 3.42 μΩ cm for 673 K conventionally H2 annealed wires. This resistivity value for the new process wires was about 16% lower than the value for wires annealed at 573 K and 13% lower than the value for the wires annealed at 673 K by the conventional H2 annealing process. The substantial resistivity decrease in the new process Cu wires is mainly attributed to uniform grain size coarsening and high (111) orientation effects by the high temperature and high rate heating, while the resistivity increase at higher heating temperatures above 923 K for new process wires is mainly attributed to the reaction between Cu and Ta/TaN barriers; the greater the extent of the reaction, the higher the resistivity.