Correlation between interface nitrogen and the fixed charge in thermally nitrided silicon dioxide on silicon

摘要

Silicon dioxide layers of 250 Aring; thick were grown on Si at 1000thinsp;deg;C in a dry O2/TCA ambient. Thermal nitridation of the samples was performed in a pure ammonia ambient at temperatures from 900 to 1100thinsp;deg;C with one hour time intervals up to a maximum of 4 h. The fixed charge state densities at the interface of the samples were determined from high frequencyChyphen;Vmeasurements, and the breakdown fields fromIhyphen;Vcurves. Secondary ion mass spectroscopy depth profiles show low levels of contaminants, and high levels of nitrogen at the interface for samples annealed at temperature greater than or equal to 1000thinsp;deg;C and for periods longer than 2 h. Post metal annealing of the nitrided samples appears to help in reducing the trapped charges. Better quality films with lowerQfandVFBshifts, and higher breakdown fields were achieved for samples annealed at 1100thinsp;deg;C. Metalhyphen;oxidehyphen;semiconductor device quality nitrided films with aQfof 1010/cm2were achieved by optimizing the process conditions at 1100thinsp;deg;C. The fixed charge build up for lower nitridation temperatures (1000thinsp;deg;C) and times (2 h)is due to the dissociation of Simdash;O bonds in the presence of hydrogen, and is in accordance with the earlier results in the literature. However, the reduction in the fixed charge buildup at 1100thinsp;deg;C, we believe, is due to the increased levels of nitrogen.