The effects of dopants on surface-energy-driven secondary grain growth in silicon films

The effects of phosphorus, arsenic, and boron on surface-energy-driven secondary grain growth (SEDSGG) in thin polycrystalline silicon films have been investigated. At concentrations at or above 5×10²⁰ cm ^-3, phosphorus and arsenic were found to markedly enhance SEDSGG while boron had little effect. However, codoping with phosphorous and boron or arsenic and boron lead to compensation (reduction or elimination) of the enhancement effect. The kinetics of SEDSGG were analyzed using transmission electron microscopy. In order to identify electronic as well as segregation effects of dopants on the kinetics of SEDSGG, electron concentrations in the Si films were determined from Hall measurements and dopant segregation was directly measured using scanning transmission electron microscopy and energy-dispersive x-ray analysis. Analogous to normal grain growth, dopant-induced enhancement of SEDSGG can be explained in terms of an increased grain-boundary atomic mobility due to changes in point-defect concentrations resulting from changes in the Fermi level. The effects of codoping on segregation of dopants at grain boundaries was found to have no appreciable effect on the rate of SEDSGG.