CHARACTERIZATION OF THE BORON DOPING PROCESSUSING BORON NITRIDE SOLID SOURCE DIFFUSION
CASTRO, SUSANA PATRICIA. Characterization of the Boron Doping Process UsingBoron Nitride Solid Source DiffusionThe purpose of this research has been to develop an optimum process for the borondoping of implants and polysilicon gates of metal-oxide-semiconductor (MOS) devices.An experimental design was constructed to determine the effects of diffusiontemperature, time, and ambient on characteristics of the doping process. A temperaturerange of 800 to 1000 degrees Celsius was studied with a diffusion time between 10 and60 minutes. Two diffusion ambients were used for doping processes, a pure nitrogenambient and a nitrogen-oxygen gaseous mixture. Device wafers were fabricated, and thetesting of MOS capacitors and van der Pauw test structures was performed to determinethe effect of diffusion conditions on flatband voltage and poly gate doping. Materialscharacterization techniques were used on monitor wafers for each diffusion process todetermine the wafer structure formed for each process and evaluate the effectiveness ofthe deglaze etch. The processes that resulted in the best device characteristics withoutsuffering from significant poly depletion effects and flatband voltage shifts were wafersdoped at 800 degrees Celsius in a pure nitrogen atmosphere for 20 minutes and 45minutes. The presence of oxygen in the atmosphere caused the depletion of boron fromthe Si wafer surface. The formation of the Si-B phase only occurred on devices processedat 1000 degrees Celsius. The deglaze process used in this experiment did not fullyremove this layer, and thus all devices doped at this temperature were seriously degraded.
Advisor:Dennis Maher, PhD; Richard Kuehn; Nadia El-Masry
School Location:USA - North Carolina
Source Type:Master's Thesis
Keywords:material science and engineering
Date of Publication:05/26/1999