Drift of Arsenic in SiO2 in a Lamp Furnace With a Built-In Temperature Gradient

Abstract

ABSTRACTWe have found that arsenic implanted into SiO2 segregates at high temperatures in an oxygen-free ambient into spherical, As-rich inclusions of 50 to 500A in diameter. The phase separation prevents diffusion of arsenic, even at temperatures as high as 1400 °C. However, the As-rich inclusions or droplets can be easily moved in a temperature gradient. They migrate towards the heat source at a rate of 2300A /hour in a gradient of 0.14 °C/μm, at 1405 °C, permitting their efficient removal from the oxide and into silicon. We propose a model to explain the dependence of droplet velocity on their size.