Evaluation of Cu-TSV Barrier Materials as a Solution to Copper Protrusion

Abstract

The development of three-dimensional large-scale integration is technically contingent upon the optimization of through-silicon via (TSV) performance. One of the intriguing challenges in the fabrication of Cu-TSV is the minimization of copper protrusion after heat treatment of TSV or any thermal cycle. Plastic behavior of copper in the temperature range of the annealing process causes the copper to protrude out of the via and damage the upper layers. Since using copper and silicon as the main constituents of the Cu-TSV is inevitable, the best solution to the copper protrusion seems to be confined to finding the best material for the barrier. The barrier is basically a liner preventing copper diffusion into the silicon. However, the material of the barrier must be selected wisely in order to assign multiple tasks to it, including the prevention of the copper protrusion. In this paper, the effects of the barrier properties on copper protrusion are evaluated, and the most proper materials for the barrier of Cu-TSV are suggested. A physical explanation of the protrusion phenomenon and the way that barrier material can minimize the protrusion are also presented.