Production of ions from solids using chemically assisted sputtering

Abstract

Boron ions are universally used as a p-type dopant for ion implantation of silicon wafers. In today’s technology, ions are produced from gases in a hot filament magnetron plasma, known as the Freeman ion source, using BF3 as a feedstock. Two problems are that the hot filament corrodes in the fluoride environment and the BF3 is quite toxic. In order to overcome these limitations, we have developed a cold cathode magnetron source which uses a conductive boride cathode liner (B4C and B6Si have been used successfully), and a nontoxic gas feed (such as CF4 or SF6), which produces boron ion fraction yields as high as 15% in beam extraction experiments performed on a low voltage ion source test stand. This is comparable to the performance obtained using a Freeman source and BF3 feed gas.