The influence of free-carrier absorption on the rapid thermal sintering process

In rapid-thermal-annealing (RTA) technology, the sample temperature is dependent on the radiation spectrum of the light source and the optical absorption properties of the samples. This study is concerned with the effects of an n+ -polysilicon layer on n+ -p junction leakage properties and on Al-metallization grain size. For a tungsten-halogen lamp anneal, the temperature increase (140°C) of samples with n+ -polysilicon is considerably higher than that of samples without, because of free-carrier absorption in the n+ -polysilicon layer. On the other hand, for long-wavelength arc lamps, free-carrier absorption in the n+ -polysilicon layer is significantly reduced; a temperature difference of only 40°C was observed between sample wafers with and without an n+ - polysilicon layer. Therefore the use of the long-wavelength arc lamp is more desirable for an Al sintering application.