Lateral growth control in excimer laser crystallized polysilicon

The control of the structural properties of polysilicon obtained by excimer laser crystallization has become of great importance to further develop th e polysilicon thin-film transistors technology. The most attractive crystal lization regime is the so-called super lateral growth (SLG), characterized, however, by a very narrow energy density window and a strongly non-uniform grain size distribution. Tn this work we have investigated several approac hes to achieve a control of the lateral growth mechanism through lateral th ermal gradients, established by the opportune spatial modulation of the hea ting. To this purpose, three different patterned capping layers have been u sed: anti-reflective (SiO2), heat-sink (silicon nitride) and reflective (me tal) overlayers. For all three types of overlayers, when the conditions to trigger the lateral growth mechanism are achieved, a band of oriented grain s (1-2 mu m wide) appears at the boundary between capped and uncapped regio n and growth extending in the more heated region. Among the different appro ach the use of reflective overlayers appears promising and further engineer ing of this process is in progress. (C) 1999 Elsevier Science S.A. All righ ts reserved.