Microstructure and Texture of Electrodeposited Cu on TiN Thin Films without a Cu Seed Layer

摘要

Very Large Scale Integrated devices (VLSI) demand the use of the lower resistivity metal for the interconnection of devices. Copper, one of the metals used for this purpose, has excellent conductivity and electromigration resistance properties. The change from aluminum to copper as the preferred metal for connecting the chip to the circuit requires an efficient barrier to avoid any copper diffusion into the semiconductor material. The transition metal nitride, TiN, is known as diffusion barrier because of the low diffusion rate of copper through it. But TiN thin films do not have a good conductivity for copper electrodeposition. Therefore, to have copper electrodeposition, one requires a seed layer over TiN thin films. Instead of the general vapor deposited seed layer process on TiN films, we used palladium chloride easily to promote copper electroplating on TiN films before processing. The grain size of the deposited layer was decreased, the adhesion and growth rate were increased, and surface roughness of this layer was modified by using the palladium chloride. The textures of the copper electrodeposited layers under the various conditions were random.