THE ION-MATRIX SHEATH AROUND A ROUND HOLE

The problem of plasma source ion implantation for a deep, plasma-fille d, cylindrical hole in a flat plate is considered. The structure of th e ion-matrix sheath resulting from the application of a zero-rise-time , negative-voltage pulse to the target is computed. Solutions for the potential structure in and around the hole are presented. It is found that the sheath does not conform completely to the hole until the radi us of the hole is larger than the ion-matrix overlap length. ion traje ctories across the sheath are found to impact upon the side wails of t he hole at glancing angles, a situation that is unfavourable to implan tation.