A new model to explain the colours generated on the surface of ion implanted silicon wafers

The surface of ion implanted silicon may exhibit various bright colours when implanted under particular high dose conditions. For some scanning systems these colours may be in the form of distinct colour bands. The mechanism of colour generation is explained. The observed colour is shown to be related to the existence and thickness of an amorphous silicon layer created by the implantation process. Different colour generation mechanisms apply when the amorphous layer is buried and when it is continuous to the surface. The colour generation model explained shows that the commonly observed 'milkiness' condition, often associated with amorphous threshold determination, is a special case of surface colour generation in ion implanted silicon. (author)