Electrical and structural properties of polycrystalline silicon

Polycrystalline silicon is used today for many thin film applications, from microelectronics to solar cells, and has been the subject of intense research for almost three decades. However, important questions remain about the structural and electrical properties of polycrystalline silicon, especially relevant now as microelectronic device dimensions scale toward the average grain size of polycrystalline silicon. Particularly elusive has been an understanding of how individual grain boundary properties determine the overall properties of the film, such as electrical resistivity. This work links the structural and electrical properties of thin polycrystalline silicon films at the level of individual grains.; A four point "transparent probe" technique was developed which allowed a small number of grains to be isolated and measured electrically in test structures which can be nondestructively prepared for direct imaging in a transmission electron microscope (TEM). By measuring the temperature dependence of electrical resistance in many test structures, the distribution of individual grain boundary activation energies for resistance was determined. After electrical measurements, grains in the test regions were imaged by TEM. Grain size, shape and crystallographic grain boundary character were measured and the distribution of relative grain misorientations was found. Measured boundaries were compared to "coincident site lattice" (CSL) related boundaries whose character has been the subject of single boundary studies. Single grain boundaries were characterized both electrically and structurally. Electrical results from the transparent probe structures were compared with standard energy band theory developed for blanket film properties and with results from a Monte Carlo model of a network of thermally activated resistors. These results demonstrate how a distribution of grain structures and orientations fundamentally determines the electrical properties of the blanket film.