Polycrystalline silicon diffusion

One of the most widely used materials for the fabrication of modern VLSI circuits is polycrystalline silicon, commonly referred to as polysilicon. It is used for the gate electrode in metal oxide semiconductor (MOS) devices, for the fabrication of high value resistors, for diffusion sources to form shallow junctions, for conduction lines, and for ensuring ohmic contact between crystalline silicon substrates and overlying metallization structures. 

In this paper, we have given a summary of some of the aspects of the work done in our laboratory on hydrogen passivation in polycrystalline silicon ribbon. We have shown that the dominant defects being passivated are dislocations, that many of the dislocation-related defects can be passivated quite readily using a Kaufman ion source, and that passivation can proceed to depths > 200 pm in some cases with diffusivities down dislocation arrays > 10- cm /sec. Several examples have been chosen to demonstrate the enormous utility of the EBIC technique in studying passivation. 

Figures 4, 5 and 6 show examples of normalized experimental pole figures. For Fig. 4 the material is a TiN fine-grained polycrystalline thin film. Such thin films, which are produced by a physical vapor deposition (PVD) method, are used in microelectronics as diffusion barriers between the silicon from one side and the aluminum current lines on the other side. From the (111) and (200) pole figures one can easily recognize that nearly all the crystallites have a (111) crystal direction parallel to C, the normal to the specimen, and are uniformly arranged around this direction. This corresponds to a so-called fiber texture.

Self-diffusion coefficients of nitrogen in polycrystalline alpha- and beta-silicon nitride were measured by using a gas-solid isotope exchange technique with as a tracer at 1200 to 14IOC. The diffusion coefficients for single-crystal grains could be expressed as ... 

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