Simulation of copper electroplating fill process of through silicon via

Abstract

A finite element model which includes fluid flow, transport by diffusion, migration and convection, multiple species, and reactions is established to simulate the copper electrochemical deposition process in through silicon via (TSV) trench. The effects of fluid flow of the bulk copper electrolyte on the micro TSV trench have been investigated. The copper plating process in different TSV trench geometries in terms of straight and tapered TSV trenches with different aspect ratios is studied with the numerical simulation. The copper ions concentration distribution and shape evolution during copper deposition process are obtained through the finite element modeling with a moving mesh technology. The effects of pulse current on the electrochemical deposition process are investigated by applied different current waveforms. From the simulation results, it is found that the fluid flow of the bulk copper electrolyte has significant effects on the top of the TSV trench and it will speed up the convection mass transfer of copper ions and plating velocity, but the effects at the bottom of TSV trench is minimal especially when the aspect ratios are large. The necking phenomenon becomes serious with the aspect ratio of TSV trench increasing from 1 to 4. It will bring void defects in the copper via and may affect the reliability performance of the package. The necking phenomenon of tapped TSV structure is slightly smaller or larger than the straight trench. The copper deposition becomes uniform when the pulse current is introduced.