High Concentration Arsenic Diffusion in Silicon from a Doped Oxide Source

Abstract

The properties of As‐doped and As‐doped diffusion sources as a function of the O2 concentration in a horizontal, open‐tube deposition chamber are examined. The effect of the Ge doping in the oxide is to enhance the etch rate and to reduce incorporated during the oxidation of AsH3. The elemental As thus formed diffuses more rapidly than in the oxide, thus enhancing the transport of As across the Si‐oxide interface. A prediffusion H2 anneal of the oxide is shown to produce a similar effect. Control of the source doping by varying the O2 concentration in the deposition chamber, . is shown to result in diffusions where the sheet resistance, Rs, varies as . In terms of the molecular fraction of As in the oxide, . RS is shown to decrease with time as . For shorter times the diffusion of As is complicated by the changing surface concentration of the electrically active fraction of As. Singly diffused As profiles in Si are shown to be described by the solutions to the diffusion equation with a concentration‐dependent diffusion coefficient. However, the preanneal in H2 is shown to cause the subsequently diffused As to have an anomalous electrical profile.