Overview of the Use of Copper Interconnects in the Semiconductor Industry

5 Damascene Process 5 History of Copper Interconnects 6 Damascene Process Steps 6 State of the Art in ECD 6 Electrochemical Deposition (ECD) 8 Basic ECD 11 V-I Curves 12 Uniformity 14 Boundary Layer 14 Conductivity 15 Bath Chemistry and Plating Waveforms 16 Superfilling 17 Morphology 17 A Look to the Future c o n t e n t s Interconnects in integrated circuits distribute clock and other signals and provide power/ground to the various integrated circuits. There are three types of interconnects: local, intermediate, and global. • Local interconnects consist of very thin lines, connecting gates, and transistors within a functional block. They usually span only a few gates and occupy first and, sometimes, second metal layers. • Intermediate interconnects are wider and taller than local interconnects in order to provide lower resistance; intermediate wiring provides clock and signal distribution within a functional block with typical lengths up to 3 to 4 mm. • Global interconnects provide clock and signal distribution between the functional blocks and deliver power/ground to all functions. Global interconnects occupy the top one or two layers, and they are longer than 4 mm—as long as half the chip perimeter. It is critical that low-resistivity global interconnects be used as the bias voltage decreases and the total current consumption of the chip increases [1]. Overview of the Use of Copper Interconnects in the Semiconductor Industry Annabelle Pratt, Ph.D., Advanced Energy Industries, Inc.