Metal contamination monitoring in ion implantation technology

In this paper we report the main results obtained through systematic monitoring of metal contamination level on high current ion implanters. The effects of metal contamination on semiconductor devices include oxide degradation, increased leakage current of p-n junctions and reduced minority carrier lifetime. The Surface Photo Voltage (SPV) technique is employed to quantify iron contamination on monitor wafers. The introduction of contamination control charts (iron concentration and diffusion length parameters) for ion implanters is effective in determining some important causes of contamination increase on implanted monitors: silicon-coating progressive erosion of the machine loading disk and specific periodic maintenance performed on the equipment. The results of these analyses allowed us to establish the equipment's disk replacement frequency and to determine the correct requalification procedure of machines after maintenance.