Dopant Activation, Carrier Mobility, and TEM Studies in Polycrystalline Silicon Films

Polycrystalline silicon films, deposited by low‐pressure chemical vapor deposition at 570° and 620°C, and doped with phosphorus by ion implantation, have been studied in terms of: dopant activation, carrier Hall mobility, and microstructure, as a function of the annealing temperature. Higher activation and carrier mobility were obtained on samples deposited at lower temperature, which were amorphous [by x‐ray diffraction and transmission electron microscopy (TEM)] after the deposition step, in contrast with those deposited at higher temperature, which were polycrystalline. Transmission electron microscopy observations on a cross section showed a better recrystallization of the amorphous films during a high‐temperature step, and mean grain size values which agree qualitatively with those calculated from grain boundary mobilities.