Preparation of high-purity gallium from semiconductor fabrication waste

This review summarizes the results of systematic studies aimed at developing processes for the preparation of high-purity gallium from semiconductor fabrication waste. A classification is proposed for Gacontaining waste materials according to the host and impurity compositions. We compare the efficiencies of different processes for the fine purification of crude gallium recovered from waste materials: wet-chemical processing, vacuum heat treatment, filtration, electrorefining, and directional solidification. Taking into account the behavior of impurities during the purification process and the nature of the waste materials, we have developed a multistep, environmentally safe process for preparing high-purity (99.9999%) gallium from unconventional raw materials. The product of this process compares well with gallium produced from conventional raw materials. We demonstrate that the use of semiconductor fabrication wastes as raw materials in large-scale-production of high-purity gallium and related microelectronic products is a commercially viable approach.