Arsenic drift in SiO sub 2: Temperature, dose and thermal gradient effects.

Thermomigration of arsenic in SiO sub 2 in a temperature gradient was recently reported. This technique for dopant movement from SiO sub 2 into Si creates an efficient oxide diffusion source, and is the only known method of forming buried n sup + conductive layers in single crystalline Si films thicker than 5micron formed on oxidized single crystalline Si substrates. Such structures are useful for high voltage and/or high power devices. Our knowledge of the arsenic drift behavior is extended here, and shows an Arrhenius dependence of drift velocity on temperature in the range 1250 to 1405C, no dependence on dose in the range 3x10 sup 15 to 3x10 sup 16 cm sup -2, and a linear dependence on the thermal gradient. The loss of arsenic from the migrating zone by normal (Fickian) diffusion is a function of the implanted dose. Measured losses for 1000angstroms of movement range from 39% at 3x10 sup 15 cm sup -2 to