COMPARISON OF BORANOL AND SILANOL REACTIVITIES IN BORON-DOPED SIO2 CHEMICAL-VAPOR-DEPOSITION FROM TRIMETHYL BORATE AND TETRAETHYL ORTHOSILICATE

For the first time, the relative rates of consumption of surface boran ols and silanols reacting with tetraethyl orthosilicate [TEOS, Si(OCH2 CH3)4] have been measured. This comparison has direct bearing on under standing the growth of doped SiO2 films from TEOS and trimethyl borate [TMB, B(OCH3)3] sources since surface boranols and silanols are expec ted to be present during the thermal chemical vapor deposition process . The measurements were accomplished by first derivatizing a porous si lica substrate with boranols and silanols via hydrolysis of the produc ts from an initial trimethyl borate (TMB) chemisorption step. TEOS exp osures in the mTorr pressure regime were then carried out in a cold-wa ll reactor. Reaction products on the surface were identified with Four ier transform infrared spectroscopy and x-ray photoelectron spectrosco py in analysis chambers adjoining the reactor. Although TEOS does not react with SiOH at 300 K, it does react with BOH at this temperature. Using the deuterated species (SiOD and BOD) to measure the relative ra tes of hydroxyl consumption without interference from concurrent hydro xyl formation, the reaction rate constant for boranols with TEOS at 10 00 K was determined to be twice that of silanols. At 1000 K, subsequen t decomposition of the TEOS chemisorption products regenerates both BO H and SiOH.