Method to Reduce Epitaxial Autodoping and Pile up in Arsenic Sub Collector Diffusions
Original Publication Date: 1980-Aug-01
Included in the Prior Art Database: 2005-Feb-13
Eptiaxial autodoping arises from the impurity redistribution contained in the top layers of the substrate. To minimize this autodoping, therefore, it is necessary to reduce this near surface concentration of the dopant in the substrate without, at the same time, increasing the resistivity of this layer. In typical LSI (large-scale integration) substrates the dopant buried layer is formed by a capsule diffusion followed by a drive-in in an oxidation environment. For the case of the N+ subcollector used in NPN bipolars for example, the oxidation drive-in causes a pile-up of the N dopant in the silicon layers at the SiO(2)/Si interface. This pile-up is caused by the segregation of the N dopant into the silicon, which, under usual conditions of oxidation rate and diffusion, does not redisperse into the silicon.