Control of high-valued polysilicon resistors by hydrogenation techniques

The control of phosphorus-implanted polysilicon layers proves difficult in the 10–20kΩ/sq resistivity range required for biasing microstrip detectors. The sheet resistivity is mainly governed by the density of the trap states linked to grain boundaries. During plasma-assisted layer deposition, free hydrogen ions are generated, which fill up these traps, thereby significantly affecting the final resistance. This trap-filling factor depends on the backend fabrication process. Large variations of the sheet resistivity can easily be explained by a lower trap-filling level, due to the presence of a nitride capping. In this work, the effects of the direct H implantation are presented. It will be shown that the on-wafer dispersion is thereby decreased to about 5%. The metal-line screening effect is also discussed.