Effect of titanium contamination on oxygen atom recombination probability on plasma conditioned surfaces

Abstract

As the tolerances in gate dimensions in integrated circuit manufacturing become ever more stringent, plasma process conditions must be very tightly controlled. The reactor chamber wall contamination is one of the major causes of process drifts and is therefore of prime importance. Here, the authors report a study of the role of Ti contamination on an oxidized silicon surface in affecting the heterogeneous recombination coefficient of O in an O2 inductively coupled plasma reactor. Recombination coefficients were measured, using the spinning wall method, with in-situ Auger electron spectroscopy (AES) for surface analysis during plasma operation. The O-atom recombination coefficient on a Ti-free surface was found to be 0.034. After using an evaporation source to deposit a small amount of Ti on the spinning wall (17% of the atomic composition obtained from AES), the O recombination coefficient decreased to 0.022. A possible mechanism is proposed in which Ti reacts with ≡Si-O• sites that are active in recombining O, forming ≡Ti-O• sites that are less efficient for O recombination.