Thermally Induced Deformation and Stresses During Millisecond Flash Lamp Annealing

A flash lamp has been proposed for annealing wafers with diameters approaching 100 mm.
The equipment applies a pulse, with duration 0.5 ms to 20 ms, resulting in large transient thermal
gradients in the wafer. In this paper, we present a model for the thermal reaction of this process
and its effect upon the mechanical behaviour, in order to predict stresses, shape changes and to
capture practical phenomenon, such as bifurcation of deformation modes. We then use the
model to follow changes in the expected response consequent on altering process conditions, as
well as exploring important issues associated with scaling to large wafer sizes. The model is
further used to predict material yielding leading to permanent deformations. This work presents
the first description of the thermo-mechanical response of wafers to flash lamp annealing in the
millisecond time regime and is therefore fundamental to the use of this technique in the
fabrication of semiconductor devices.