The evaluation of the Harwell-Lintott industrial ion implantation machine by making silicon planar resistors

Resistors were made by implanting boron into n-type silicon in the Harwell-Lintott industrial ion implantation machine. For resistors implanted at low dose rates, variations in resistors values were limited by factors other than the implantation to +or-21/2% on a slice and +or-5% for slices processed in the same batch. Higher dose rates led to similar variations if the slices were annealed at a high temperature (800 degrees C) and the slices were in a good thermal contact with the backing plate during the implantation. When, however, no special effort was made to dissipate the heat generated in the slices during the implantation, and the slices were subsequently annealed at only 500 degrees C, there were nonuniformities across slices and from slice to slice. This was due to the slices heating up. In many applications these effects are not serious, as high temperature anneals or low doses are used. In other applications it is necessary to ensure good thermal contact between the slice and the backing plate.