Bench top dual mode eCMP polisher with multi sensing metrology

摘要

A traditional CMP tool is designed to achieve the planarization process across the wafer via a down-force polishing effect. In doing so, the wafer is pressed onto a rotating polishing pad and a slurry material is applied. The traditional CMP process can cause delamination and fracture of low-k dielectrics that are soft and porous. A new alternative a low down-force process of electro-polishing or eCMP is being considered, in which a current is run from a conducting surface, through a conducting liquid and into an electrode. Under proper conditions, metal can be removed from the wafer surface into solution. As the eCMP is not a mature technology, there are no standard consumables on the market. To develop slurries, pad, particles, conditioners, etc. we have developed a multifunctional bench-top eCMP polisher mod. eCP-4. The eCP-4 can be used to run both conductive and non-conductive pads. The tool can be used to do polishing in both constant current and constant voltage modes. It has a precise down-force servo-control from 0.05 to 10 psi. The eCP-4 polisher is equipped with multi-sensing metrology which measures in-situ friction force and coefficient in both wafer-pad and conditioner-pad interfaces, contact acoustic emission, applied voltage and current, temperature, pad wear at a 100 kHz data acquisition rate. The same tool can also be used for a regular CMP, which enables to use CMP and eCMP sequentially to completely clear the barrier after copper removal. This paper covers the capabilities of the bench-top eCMP polisher with both conductive and non-conductive pads. We present the data obtained on the eCMP tool and explain the benefits of multi-sensing metrology to develop novel processes and materials for eCMP.