Segregation and drift of arsenic in SiO sub 2 under the influence of a temperature gradient.

We have found that arsenic implanted into SiO sub 2 segregates at high temperatures into spherical, As-rich droplets of 50 to 500angstroms in diameter, provided that there is no free oxygen present in the SiO sub 2 and the initial As concentration exceeds 1 at. %. The phase separation prevents diffusion of arsenic, even at temperatures as high as 1400C. We have discovered, however, that the As droplets can be easily moved in a temperature gradient. The droplets migrate towards the heat source at a rate of 2300angstroms/hour in a gradient of 0.14C/micron, at 1405C, permitting their efficient removal from the oxide and into silicon.