Evaluation of electrode materials for ion implanters

A quantitative evaluation of electrical breakdown properties of seventeen different materials, including metals, composite materials and graphites, is presented. The microscopic field amplification factor, /spl beta/, of clean electrodes is found to vary by an order of magnitude. The breakdown history of samples, subjected to lifetime tests by repetitively causing arcing from the sample surface under controlled conditions, shows that coated graphites exhibit deterioration after few arcing events, while vitreous impregnated graphites (VGI) show stable breakdown voltage characteristics. For ion implantation, electrode material selection demands low /spl beta/ and long electrode lifetime with stable operating characteristics. We find that certain VGI graphites with metallic breakdown properties are well suited for electrode material.