BORON BY DIFFUSION IN SILICON

Abstract approved Redacted for Privacy (Major professor).. A technique was investigated in which a silicon crystal was used as a very sensitive detector of sub-nanogram quantities of boron. The unknown quantity of boron was spread uniformly on the surface of an n-type silicon wafer which was then baked for diffusion. The measured depth of the p-n junction was related to the concentration distribution and the quantity of boron per cm2 of sili-con surface was obtained from curves for a Gaussian distribution. This method can detect quantities of boron of the order of 10-14 gms. /cm 2 which is far below the limit of sensitivity of any other method. An attempt was made to use this boron detection method for obtaining the distribution profile of boron in silicon dioxide layers. But the use of HF for layer sectioning was found to lead to a loss of 1 a part of the boron presumably as BF3 gas. The only way this method could be used for this purpose is either by recovering com-pletely the boron from the HF etch by some chemical process or by sectioning the layers in a manner such that the sectioning agent does not react with boron to form a compound which is lost as gas