THE EFFECT OF ANNEALING ON RESISTIVITY OF LOW-PRESSURE CHEMICAL VAPOR-DEPOSITED TITANIUM DIBORIDE

The correlation between the resistivity of TiB2 and the chemical vapor deposition parameters and subsequent annealing temperature have been studied. The films deposited from TiCl4 and B2H6 above 600-degrees-C are found to be nearly stoichiometric TiB2 with a resistivity of 250-mu-OMEGA cm +/- 20%, while those deposited below 600-degrees-C are found to contain excess boron, and exhibit a higher resistivity. The resistivity of the films is observed to be independent of thickness in the thickness range from 15 to 550 nm. After high-temperature rapid thermal annealing (> 1000-degrees-C), the resistivity is reduced to as low as 36-mu-OMEGA cm. The grain size in annealed films increases exponentially with temperature. The conductivity and the Hall mobility of the samples increase linearly with the grain size. The activation energy of grain growth, conductivity, and Hall mobility was found to be the same, 1.6-1.7 eV. From these results, it is evident that the carrier mobility of TiB2 is dominated by grain boundary scattering. The lower limit for resistivity of chemical vapor deposited TiB2 films is expected to be attainable only after annealing at temperatures approaching 1300-degrees-C.