Diffusion of ion-implanted As in SiO2

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Abstract
We investigated the diffusion of ion‐implanted As in SiO2 with Rutherford backscattering spectrometry. By applying different annealing ambients and also encapsulating with a Si3N4 layer, we were able to distinguish three types of diffusion for implanted As in SiO2. These are correlated to two chemical states of As in SiO2. One state, with As completely immobile in SiO2, is typical for implanted As and occurs when no extra oxygen is supplied during annealing. This type of As is associated with As on oxygen sites in the SiO2 network. When extra oxygen is supplied during annealing, As is incorporated on Si sites and exhibits the normal diffusion coefficient of As in SiO2. Diffusion occurs by a mobile arsenic‐oxygen complex formed by a reaction with the extra oxygen. When annealing is carried out in an O2/H2O mixture, enhanced diffusion of As is observed; this is attributed to the introduction of hydroxyl groups in the SiO2 network which tend to weaken the structure. When, in addition to the As, P is also implanted, As becomes immobile in all annealing ambients.